Diagnostic assays and kits for detection of folate receptor 1

ABSTRACT

The invention generally relates to antibodies that bind to human folate receptor 1 and diagnostic assays for folate receptor 1-based therapies. Methods of using the antibodies to monitor therapy are further provided.

REFERENCE TO RELATED APPLICATIONS

Related applications U.S. application Ser. No. 14/015,653, filed Aug.30, 2013, U.S. Provisional Application Nos. 61/695,791, filed Aug. 31,2012 and 61/756,254, filed Jan. 24, 2013, are herein incorporated byreference in their entireties.

REFERENCE TO A SEQUENCE LISTING SUBMITTED ELECTRONICALLY VIA EFS-WEB

The content of the electronically submitted sequence listing (Name:2921_0370003_SeqListing.txt; Size: 44,372 bytes; and Date of Creation:Oct. 23, 2015) is herein incorporated by reference in its entirety.

FIELD OF THE INVENTION

The field of this invention generally relates to antibodies that bind tohuman folate receptor 1 (FOLR1), methods of detecting FOLR1, methods ofdiagnosing and treating cancer, and diagnostic assays and kits forFOLR1-based therapies.

BACKGROUND OF THE INVENTION

Cancer is one of the leading causes of death in the developed world,with over one million people diagnosed with cancer and 500,000 deathsper year in the United States alone. Overall it is estimated that morethan 1 in 3 people will develop some form of cancer during theirlifetime. There are more than 200 different types of cancer, four ofwhich—breast, lung, colorectal, and prostate—account for over half ofall new cases (Jemal et al., 2003, Cancer J. Clin. 53:5-26).

Folate Receptor 1 (FOLR1), also known as Folate Receptor-alpha or FolateBinding Protein, is an N-glycosylated protein expressed on plasmamembrane of cells. FOLR1 has a high affinity for folic acid and forseveral reduced folic acid derivatives. FOLR1 mediates delivery of thephysiological folate, 5-methyltetrahydrofolate, to the interior ofcells.

FOLR1 is overexpressed in the vast majority of ovarian cancers, as wellas in many uterine, endometrial, pancreatic, renal, lung, and breastcancers, while the expression of FOLR1 on normal tissues is restrictedto the apical membrane of epithelial cells in the kidney proximaltubules, alveolar pneumocytes of the lung, bladder, testes, choroidplexus, and thyroid (Weitman S D, et al., Cancer Res 52: 3396-3401(1992); Antony A C, Annu Rev Nutr 16: 501-521 (1996); Kalli K R, et al.Gynecol Oncol 108: 619-626 (2008)). This expression pattern of FOLR1makes it a desirable target for FOLR1-directed cancer therapy.

Because ovarian cancer is typically asymptomatic until advanced stage,it is often diagnosed at a late stage and has poor prognosis whentreated with currently available procedures, typically chemotherapeuticdrugs after surgical de-bulking (von Gruenigen V et al., Cancer 112:2221-2227 (2008); Ayhan A et al., Am J Obstet Gynecol 196: 81 e81-86(2007); Harry V N et al., Obstet Gynecol Surv 64: 548-560 (2009)). Thusthere is a clear unmet medical need for more effective therapeutics forovarian cancers.

Some previous assays used to detect shed FOLR1 are not sufficientlyspecific to FOLR1. For example, some assays do not distinguish betweenFOLR1 and other folate receptor family members (FOLR2, 3, & 4) or reportvalues for total FBP (Folate Binding Protein). Additionally, some assaysrequire that human samples (e.g., plasma) be pre-treated with a lightacid wash step to dissociate folic acid from the receptor. Some assayresults may also have inaccuracies due to competitive effects betweenthe antibody therapy and diagnostic antibody. Additionally, manycommercially available kits are traditionally unreliable both in theirreagents, and in their lot-to-lot stability. Evaluations of these kitshave given very mixed results, and are intended for research use only.Many require that the human sample be pre-diluted before analysis toreduce the chance of false positives due to the “matrix effect.” Thus,there is a clear need for highly sensitive and accurate diagnosticassays as a companion for FOLR1-based therapies.

SUMMARY OF THE INVENTION

The present invention provides methods for detection of FOLR1 in asample and can be used, for example, to stratify patients. Thus, in oneembodiment, the invention provides a method of treating a patient havinga folate receptor 1-mediated disease comprising: (a) measuring the shedfolate receptor 1 (FOLR1) expression level or FOLR1 on a circulatingtumor cell (CTC) in a sample taken from a patient, relative to a shed orCTC FOLR1 level in a reference sample using an antibody orantigen-binding fragment thereof that does not competitively inhibit thebinding of the antibody huMov19 to FOLR1; and (b) administering to thepatient a fixed dose of an antibody or antigen-binding fragment thereofthat modulates FOLR1 activity if the patient's shed or CTC FOLR1 levelis elevated; wherein the fixed dose of the antibody or fragment thereofeffectively treats the disease or disorder.

In another embodiment, the invention provides a method of treating apatient having a FOLR1-mediated disease or disorder comprising: (a)administering to a patient having a FOLR1-mediated disease or disorder afixed dose of an antibody or antigen-binding fragment thereof thatmodulates FOLR1 activity; (b) measuring the patient's shed or CTC FOLR1expression level relative to the FOLR1 level in a reference sample usingan antibody or antigen binding fragment thereof that does notcompetitively inhibit the binding of the antibody huMov19 to FOLR1; and(c) increasing the amount or frequency of subsequent fixed doses if thepatient's shed or CTC FOLR1 level is elevated; wherein an increase(e.g., because increased cell death results in an increased release ofshed FOLR1) or decrease in FOLR1 levels of the patient is indicative oftreatment efficacy. In another embodiment, the amount or frequency ofsubsequent fixed doses is increased if the patient's shed or CTC FOLR1level is decreased.

In another embodiment, the invention provides a method of decreasingFOLR1 expression in a patient comprising: (a) measuring the shed or CTCFOLR1 level in a sample taken from a patient having a FOLR1-mediateddisease or disorder, compared to the FOLR1 level in a reference sampleusing an antibody or antigen-binding fragment thereof that does notcompetitively inhibit the binding of the antibody huMov19 to FOLR1; and(b) administering to the patient a fixed dose of an antibody orantigen-binding fragment thereof that modulates FOLR1 activity if thepatient's shed or CTC FOLR1 level is elevated; wherein theadministration of the antibody or antigen-binding fragment thereofincreases (e.g., because increased cell death results in an increasedrelease of shed FOLR1) or decreases FOLR1 of the patient.

In another embodiment, the invention provides a method of decreasingFOLR1 expression in a patient comprising: (a) administering to a patienthaving a FOLR1-mediated disease or disorder a fixed dose of an antibodyor antigen-binding fragment thereof that modulates FOLR1 activity; (b)measuring the patient's shed or CTC FOLR1 level relative to the FOLR1level in a reference sample; and (c) increasing the amount or frequencyof subsequent fixed doses if the patient's shed or CTC FOLR1 level iselevated; wherein the administration of the antibody or antigen-bindingfragment thereof increases (e.g., because increased cell death resultsin an increased release of shed FOLR1) or decreases FOLR1 levels in thepatient.

In one embodiment, the disease is cancer. In another embodiment, thecancer is a FOLR1 elevated cancer selected from the group consisting of:ovarian, non-small cell lung cancer, uterine, endometrial, pancreatic,renal, lung, and breast cancer. In another embodiment, the cancer isovarian cancer that is platinum resistant or platinum refractory.

The invention also provides a method of monitoring therapeutic efficacyof a fixed dose of an antibody or antigen-binding fragment thereof thatmodulates FOLR1 activity in a patient comprising: (a) measuring a firstshed or CTC FOLR1 level in a sample taken from a patient having aFOLR1-mediated disease or disorder using an antibody or antigen-bindingfragment thereof that does not competitively inhibit the binding of theantibody huMov19 to FOLR1; (b) administering to the patient a fixed doseof an antibody or antigen-binding fragment thereof that modulates FOLR1activity; (c) measuring a second shed or CTC FOLR1 level in a sampletaken from the patient following antibody administration using anantibody or antigen-binding fragment thereof that does not competitivelyinhibit the binding of the antibody huMov19 to FOLR1; and (d) comparingthe second FOLR1 level to the first FOLR1 level; wherein an increase(e.g., because increased cell death results in an increased release ofshed FOLR1) or decrease between the first and second FOLR1 scoresindicates therapeutic efficacy.

In one embodiment, the FOLR1 expression level is measured in a bodilyfluid. In another embodiment, the bodily fluid is ascites fluid. Inanother embodiment, the bodily fluid is serum, blood, or plasma. Inanother embodiment, the FOLR1 expression level is measured in aperipheral blood sample.

In one embodiment, the patient has cancer. In another embodiment, thecancer is a FOLR1 elevated cancer selected from the group consisting ofovarian, non-small cell lung cancer, uterine, endometrial, pancreatic,renal, lung, and breast cancer. In another embodiment, the cancer isovarian cancer that is platinum resistant or platinum refractory.

In one embodiment, the FOLR1 expression is measured using at least oneadditional anti-FOLR1 antibody or antigen-binding fragment thereof. Inanother embodiment, the FOLR1 expression is measured using twoanti-FOLR1 antibodies or antigen-binding fragments thereof. In anotherembodiment, the In another embodiment, the antibody is a murine,chimeric, humanized, or human antibody. In another embodiment, theantibody or antigen-binding fragment thereof binds to a human folatereceptor 1 with a Kd of about 1.0 to about 10 nM. In another embodiment,the antibody or antigen-binding fragment thereof binds to a human folatereceptor 1 with a Kd of about 0.5 nM to about 5 nM. In anotherembodiment, the binding affinity is measured by cytometry, Biacore,ELISA, or radioimmunoassay. In another embodiment, the cytometry is flowcytometry.

In one embodiment, the antibody or antigen-binding fragment thereof doesnot bind folate receptor 2 or folate receptor 3.

In one embodiment, the at least one antibody or antigen-binding fragmentthereof is bound to a solid support. In another embodiment, the at leastone antibody or antigen-binding fragment thereof is bound to amicrotiter plate. In another embodiment, the at least one antibody orantigen-binding fragment thereof comprises a detection agent. In anotherembodiment, the detection agent is a chromogenic detection agent, afluorogenic detection agent, an enzymatic detection agent, or anelectrochemiluminescent detection agent. In another embodiment, thedetection agent is horseradish peroxidase (HRP).

In one embodiment, the FOLR1 levels are determined using an enzymelinked immunosorbent assay (ELISA), or cytometry (e.g., flow cytometry).In another embodiment, the ELISA is a sandwich ELISA.

In one embodiment, the at least one antibody or antigen-binding fragmentthereof specifically binds to the same FOLR1 epitope as an antibodyselected from the group consisting of: (a) an antibody comprising thepolypeptide of SEQ ID NO:25 and the polypeptide of SEQ ID NO:29; (b) anantibody comprising the polypeptide of SEQ ID NO:26 and the polypeptideof SEQ ID NO:30; (c) an antibody comprising the polypeptide of SEQ IDNO:27 and the polypeptide of SEQ ID NO:31; and (d) an antibodycomprising the polypeptide of SEQ ID NO:28 and the polypeptide of SEQ IDNO:32.

In one embodiment, the at least one antibody or antigen-binding fragmentthereof specifically binds to FOLR1, wherein the antibody or fragmentthereof competitively inhibits FOLR1 binding of an antibody selectedfrom the group consisting of: (a) an antibody comprising the polypeptideof SEQ ID NO:25 and the polypeptide of SEQ ID NO:29; (b) an antibodycomprising the polypeptide of SEQ ID NO:26 and the polypeptide of SEQ IDNO:30; (c) an antibody comprising the polypeptide of SEQ ID NO:27 andthe polypeptide of SEQ ID NO:31; and (d) an antibody comprising thepolypeptide of SEQ ID NO:28 and the polypeptide of SEQ ID NO:32.

In one embodiment, the at least one antibody or antigen-binding fragmentthereof specifically binds to FOLR1, wherein the antibody comprisespolypeptide sequences selected from the group consisting of: (a) SEQ IDNOs: 1, 2, and 3 and SEQ ID NOs: 13, 14, and 15; (b) SEQ ID NOs: 4, 5,and 6 and SEQ ID NOs: 16, 17, and 18; (c) SEQ ID NOs: 7, 8, and 9 andSEQ ID NOs: 19, 20, and 21; (d) SEQ ID NOs: 10, 11, and 12 and SEQ IDNOs: 22, 23, and 24; and (e) variants of (a) to (d) comprising 1, 2, 3,or 4 conservative amino acid substitutions.

In one embodiment, the at least one antibody or antigen-binding fragmentthereof is detectably labeled.

In one embodiment, the administered antibody comprises the FOLR1antibody huMov19.

In one embodiment, the huMov19 is administered as an antibodymaytansinoid conjugate. In one embodiment the antibody maytansinoidconjugate comprises the maytansinoid DM4 and the cleavable sulfo-SPDBlinker (IMGN853).

The invention also provides a method of treating a patient having aFOLR1-mediated disease or disorder comprising: (a) administering to apatient having a FOLR1-mediated disease or disorder a fixed dose of anantibody or antigen-binding fragment thereof that modulates FOLR1activity; (b) submitting a sample taken from the patient for measurementof a FOLR1 expression level; (c) determining from the results of themeasurement whether the patient's shed or CTC FOLR1 level is elevatedrelative to the FOLR1 level in a reference sample; and, (d) increasingthe amount or frequency of subsequent fixed doses if the patient's shedor CTC FOLR1 level is elevated.

The invention also provides a method of treating a patient having aFOLR1-mediated disease or disorder comprising: (a) administering to apatient having a FOLR1-mediated disease or disorder a fixed dose of anantibody or antigen-binding fragment thereof that modulates FOLR1activity; (b) submitting a sample taken from the patient for measurementof a shed or CTC FOLR1 level and comparison to a FOLR1 level in areference sample; and (c) increasing the amount or frequency ofsubsequent fixed doses if the patient's shed or CTC FOLR1 level iselevated; wherein an increase (e.g., because increased cell deathresults in an increased release of shed FOLR1) or decrease in the FOLR1levels of the patient is indicative of treatment efficacy.

In one embodiment, the administered antibody comprises the FOLR1antibody huMov19. In another embodiment, the huMov19 is administered asan antibody maytansinoid conjugate. In one embodiment the antibodymaytansinoid conjugated comprises the maytansinoid DM4 and the cleavablesulfo-SPDB linker (IMGN853).

The invention also provides a method of treating a patient having aFOLR1-mediated disease or disorder comprising: (a) obtaining a samplefrom a patient having a FOLR1-mediated disease or disorder, where thepatient has received a fixed dose of an antibody or antigen-bindingfragment thereof that modulates FOLR1 activity; (b) measuring a shed orCTC FOLR1 level from the sample using an antibody or antigen-bindingfragment thereof that does not competitively inhibit the binding of theantibody huMov19 to FOLR1; (c) determining whether the patient's shed orCTC FOLR1 level is elevated relative to a FOLR1 level in a referencesample; (d) instructing a healthcare provider to increase the amount orfrequency of subsequent fixed doses if the patient's shed or CTC FOLR1level is elevated; wherein an increase (e.g., because increased celldeath results in an increased release of shed FOLR1) or decrease in theFOLR1 of the patient is indicative of treatment efficacy.

The invention also provides an immunoassay kit for detecting shed or CTCFOLR1 in a sample, the kit comprising: (a) a capture antibody againsthuman FOLR1, wherein the capture antibody or antigen-binding fragmentthereof does not competitively inhibit the binding of huMov19 to FOLR1,and (b) a detection reagent. In another embodiment, the kit furthercomprises a solid support for the capture reagent. In anotherembodiment, the capture reagent is immobilized on the solid support. Inanother embodiment, the capture reagent is coated on a microtiter plate.In another embodiment, the detection reagent is a second FOLR1 antibody.In another embodiment, the first and/or second FOLR1 antibody comprisespolypeptide sequences selected from the group consisting of: (a) SEQ IDNOs: 1, 2, and 3 and SEQ ID NOs: 13, 14, and 15; (b) SEQ ID NOs: 4, 5,and 6 and SEQ ID NOs: 16, 17, and 18; (c) SEQ ID NOs: 7, 8, and 9 andSEQ ID NOs: 19, 20, and 21; (d) SEQ ID NOs: 10, 11, and 12 and SEQ IDNOs: 22, 23, and 24; and (e) variants of (a) to (d) comprising 1, 2, 3,or 4 conservative amino acid substitutions.

In one embodiment, the detection reagent is detected using a speciesspecific antibody. In another embodiment, the kit further comprises adetection means for the detectable antibodies. In another embodiment,the detection means is colorimetric. In another embodiment, the kitfurther comprises a FOLR1 polypeptide as an antigen standard. In anotherembodiment, the FOLR1 polypeptide is FOLR1-Fc.

The invention also provides an antibody or antigen-binding fragmentthereof that specifically binds to the same FOLR1 epitope as an antibodyselected from the group consisting of: (a) an antibody comprising thepolypeptide of SEQ ID NO:25 and the polypeptide of SEQ ID NO:29; (b) anantibody comprising the polypeptide of SEQ ID NO:26 and the polypeptideof SEQ ID NO:30; (c) an antibody comprising the polypeptide of SEQ IDNO:27 and the polypeptide of SEQ ID NO:31; and (d) an antibodycomprising the polypeptide of SEQ ID NO:28 and the polypeptide of SEQ IDNO:32.

The invention also provides an antibody or antigen-binding fragmentthereof that specifically binds to FOLR1, wherein the antibody orfragment thereof competitively inhibits binding to FOLR1 of an antibodyselected from the group consisting of: (a) an antibody comprising thepolypeptide of SEQ ID NO:25 and the polypeptide of SEQ ID NO:29; (b) anantibody comprising the polypeptide of SEQ ID NO:26 and the polypeptideof SEQ ID NO:30; (c) an antibody comprising the polypeptide of SEQ IDNO:27 and the polypeptide of SEQ ID NO:31; and (d) an antibodycomprising the polypeptide of SEQ ID NO:28 and the polypeptide of SEQ IDNO:32.

The invention also provides an antibody or antigen-binding fragmentthereof that specifically binds to FOLR1, wherein the antibody comprisespolypeptide sequences selected from the group consisting of: (a) SEQ IDNOs: 1, 2, and 3 and SEQ ID NOs: 13, 14, and 15; (b) SEQ ID NOs: 4, 5,and 6 and SEQ ID NOs: 16, 17, and 18; (c) SEQ ID NOs: 7, 8, and 9 andSEQ ID NOs: 19, 20, and 21; (d) SEQ ID NOs: 10, 11, and 12 and SEQ IDNOs: 22, 23, and 24; and (e) variants of (a) to (d) comprising 1, 2, 3,or 4 conservative amino acid substitutions.

In one embodiment, the antibody comprises polypeptide sequences that areat least 90% identical to polypeptide sequences selected from the groupconsisting of: (a) SEQ ID NO:25 and SEQ ID NO:29; (b) SEQ ID NO:26 andSEQ ID NO:30; (c) SEQ ID NO:27 and SEQ ID NO:31; and (d) SEQ ID NO:28and SEQ ID NO:32. In another embodiment, the polypeptide sequences areat least 95% identical to polypeptide sequences selected from the groupconsisting of: (a) SEQ ID NO:25 and SEQ ID NO:29; (b) SEQ ID NO:26 andSEQ ID NO:30; (c) SEQ ID NO:27 and SEQ ID NO:31; and (d) SEQ ID NO:28and SEQ ID NO:32. In another embodiment, the polypeptide sequences areat least 99% identical to polypeptide sequences selected from the groupconsisting of: (a) SEQ ID NO:25 and SEQ ID NO:29; (b) SEQ ID NO:26 andSEQ ID NO:30; (c) SEQ ID NO:27 and SEQ ID NO:31; and (d) SEQ ID NO:28and SEQ ID NO:32.

In one embodiment, the antibody or antigen-binding fragment thereof ismurine, non-human, humanized, chimeric, resurfaced, or human. In anotherembodiment, the antibody binds to human FOLR1 but not FOLR2 or FOLR3. Inanother embodiment, the antibody is a full length antibody or anantigen-binding fragment. In another embodiment, the antibody orantigen-binding fragment thereof comprises a Fab, Fab′, F(ab′)2, Fd,single chain Fv or scFv, disulfide linked Fv, V-NAR domain, IgNar,intrabody, IgGACH2, minibody, F(ab′)3, tetrabody, triabody, diabody,single-domain antibody, DVD-Ig, Fcab, mAb2, (scFv)2, or scFv-Fc.

The invention also provides a polypeptide that specifically binds FOLR1,wherein the polypeptide comprises sequences selected from the groupconsisting of: (a) SEQ ID NOs: 1, 2, and 3 and SEQ ID NOs: 13, 14, and15; (b) SEQ ID NOs: 4, 5, and 6 and SEQ ID NOs: 16, 17, and 18; (c) SEQID NOs: 7, 8, and 9 and SEQ ID NOs: 19, 20, and 21; (d) SEQ ID NOs: 10,11, and 12 and SEQ ID NOs: 22, 23, and 24; and (e) variants of (a) to(d) comprising 1, 2, 3, or 4 conservative amino acid substitutions. Inanother embodiment, the polypeptide comprises sequences that are atleast 90% identical to sequences selected from the group consisting of:(a) SEQ ID NO:25 and SEQ ID NO:29; (b) SEQ ID NO:26 and SEQ ID NO:30;(c) SEQ ID NO:27 and SEQ ID NO:31; and (d) SEQ ID NO:28 and SEQ IDNO:32. In another embodiment, the sequences are at least 95% identicalto sequences selected from the group consisting of: (a) SEQ ID NO:25 andSEQ ID NO:29; (b) SEQ ID NO:26 and SEQ ID NO:30; (c) SEQ ID NO:27 andSEQ ID NO:31; and (d) SEQ ID NO:28 and SEQ ID NO:32. In anotherembodiment, the sequences are at least 99% identical to sequencesselected from the group consisting of: (a) SEQ ID NO:25 and SEQ IDNO:29; (b) SEQ ID NO:26 and SEQ ID NO:30; (c) SEQ ID NO:27 and SEQ IDNO:31; and (d) SEQ ID NO:28 and SEQ ID NO:32.

In one embodiment, the antibody or polypeptide binds to a human folatereceptor 1 with a Kd of about 1.0 to about 10 nM. In another embodiment,the antibody or polypeptide binds to a human folate receptor 1 with a Kdof about 1.0 nM or better. In another embodiment, the binding affinityis measured by cytometry, Biacore, ELISA, or radioimmunoassay. Inanother embodiment, the cytometry is flow cytometry.

The invention also provides a method of detecting FOLR1 expression in asample comprising contacting the sample with an antibody orantigen-binding fragment thereof or polypeptide of the invention. Inanother embodiment, the antibody or antigen-binding fragment thereof isdetectably labeled. In another embodiment, the label is selected fromthe group consisting of immunofluorescent label, chemiluminescent label,phosphorescent label, enzyme label, radiolabel, avidin/biotin, colloidalgold particles, colored particles and magnetic particles. In anotherembodiment, the FOLR1 expression is determined by radioimmunoassay,Western blot assay, immunofluorescent assay, enzyme immunoassay,immunoprecipitation assay, chemiluminescent assay, orimmunohistochemical assay. In another embodiment, the FOLR1 expressionis determined using a circulating tumor cell (CTC) assay where the CTCsare enriched from a sample of blood, plasma, or serum and stained forFOLR1 expression using an antibody or antigen-binding fragment thereofof the invention. Non-limiting examples of antibodies useful for the CTCassay include FR1-9 and FR1-13. CTC assays using the antibodies of thepresent invention may be useful for identifying a subject as likely torespond to a FOLR1-based therapy.

The invention also provides an isolated cell producing an antibody orantigen-binding fragment thereof or polypeptide of the invention.

The inventions also provides a method of making an antibody orantigen-binding fragment thereof, or polypeptide of the inventioncomprising (a) culturing a cell expressing the antibody orantigen-binding fragment thereof, or polypeptide of the invention.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating cancer, wherein increased expression of FOLR1protein has been measured in a cancerous sample from the subject usingan antibody, antigen-binding fragment thereof, or polypeptide providedherein prior to administration of the active agent.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating a FOLR1-mediated disease or disorder,comprising: (a) measuring the FOLR1 protein level in a patient sampleusing an antibody, antigen-binding fragment thereof, or polypeptideprovided here; and (b) administering to the patient a fixed dose of theactive agent if the patient's FOLR1 protein level is elevated relativeto a reference FOLR1 protein level.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating a FOLR1-mediated disease or disorder,comprising: (a) administering to a patient having a FOLR1-mediateddisease or disorder a fixed dose of the active agent; (b) measuring thepatient's FOLR1 protein level using the antibody, antigen-bindingfragment thereof, or polypeptide provided herein; and (c) increasing theamount or frequency of subsequent fixed doses if the patient's FOLR1protein level is elevated relative to a reference FOLR1 protein level.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating a FOLR1-mediated disease or disorder, wherein(a) the FOLR1 protein level measured in a sample taken from a patient iscompared a reference FOLR1 protein level using an antibody,antigen-binding fragment thereof, or polypeptide provided herein; and(b) a fixed dose of the active agent is administered if the patient'sFOLR1 protein level is elevated relative to the reference FOLR1 proteinlevel, wherein the administration of the active agent decreases theFOLR1 protein level.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating a FOLR1-mediated disease or disorder, whereinFOLR1-expressing cells in a patient are decreased, wherein (a) a fixeddose of the active agent is administered to the patient; (b) the FOLR1protein level measured in a sample obtained from the patient is comparedto a reference FOLR1 protein level using an antibody, antigen-bindingfragment thereof, or polypeptide provided herein; and (c) the amount orfrequency of subsequent fixed doses is increased if the patient's FOLR1protein level is elevated relative to the reference FOLR1 protein level;wherein the administration of the active agent decreases the FOLR1protein level.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for monitoring the therapeutic efficacy of a fixed dose ofthe active agent in a patient comprising: (a) measuring a first FOLR1protein level in a sample from a patient having a FOLR1-mediated diseaseor disorder using an antibody, antigen-binding fragment thereof, orpolypeptide provided herein; (b) administering to the patient a fixeddose of the active agent; (c) measuring a second FOLR1 protein level ina sample taken from the patient following active agent administrationusing an antibody, antigen-binding fragment thereof, or polypeptideprovided herein; and (d) comparing the second FOLR1 protein level to thefirst FOLR1 protein level; wherein a decrease between the first andsecond FOLR1 protein levels indicates therapeutic efficacy.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating a FOLR1-mediated disease or disorder in apatient, comprising: (a) administering a fixed dose of the active agentto a patient having a FOLR1-mediated disease or disorder; (b) submittinga sample taken from the patient for measurement of a FOLR1 protein levelusing an antibody, antigen-binding fragment thereof, or polypeptideprovided herein; (c) determining from the results of the measurementwhether the patient's FOLR1 protein level is elevated relative to areference FOLR1 protein level; and, (d) increasing the amount and/orfrequency of subsequent fixed doses if the patient's FOLR1 protein levelis elevated relative to the reference FOLR1 protein level.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating a FOLR1-mediated disease or disorder,comprising: (a) administering a fixed dose of the active agent to apatient having a FOLR1-mediated disease or disorder; (b) submitting asample taken from the patient for measurement of a FOLR1 protein levelusing an antibody, antigen-binding fragment thereof, or polypeptideprovided herein and comparison of the measured FOLR1 protein level to areference FOLR1 protein level; and (c) increasing the amount orfrequency of subsequent fixed doses if the patient's FOLR1 protein levelis elevated relative to the reference FOLR1 protein level; wherein adecrease in the FOLR1 levels of the patient is indicative of treatmentefficacy.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating a FOLR1-mediated disease or disorder,comprising: (a) obtaining a sample from a patient having aFOLR1-mediated disease or disorder, where the patient has received afixed dose of the active agent; (b) measuring a FOLR1 protein level fromthe sample using an antibody, antigen-binding fragment thereof, orpolypeptide provided herein; (c) determining whether the patient's FOLR1protein level is elevated relative to a reference FOLR1 protein level;(d) increasing or instructing a healthcare provider to increase theamount and/or frequency of subsequent fixed doses if the patient's FOLR1protein level is elevated relative to the reference FOLR1 protein level;wherein a decrease in the FOLR1 of the patient is indicative oftreatment efficacy.

The invention also provides an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity for usein a method for treating a FOLR1-mediated disease or disorder whereinincreased expression of FOLR1 has been measured in a sample from thesubject using an antibody, antigen-binding fragment thereof, orpolypeptide provided herein prior to administration of the active agent.

In some embodiments, the measured FOLR1 protein is shed FOLR1. In someembodiments, the measured FOLR1 protein is on a circulating tumor cell.

In some embodiments, the FOLR1 protein level is measured in a bodilyfluid. In some embodiments, the bodily fluid is ascites fluid. In someembodiments, the bodily fluid is serum, blood, or plasma. In someembodiments, the FOLR1 protein level is measured in a peripheral bloodsample.

In some embodiments, the patient has cancer. In some embodiments, theFOLR1-mediated disease or disorder is cancer. In some embodiments, thecancer is a FOLR1 elevated cancer selected from the group consisting of:ovarian, non-small cell lung cancer, uterine, endometrial, pancreatic,renal, lung, and breast cancer. In some embodiments, the ovarian canceris platinum resistant or platinum refractory. In some embodiments, thelung cancer is non-small cell lung cancer (NSCLC). In some embodiments,the cancer is endometrial cancer.

In some embodiments, the FOLR1 protein level is measured using twodifferent antibodies or antigen-binding fragments thereof orpolypeptides specifically binding FOLR1. In some embodiments, theantibody, antigen-binding fragment thereof, or polypeptide used todetect FOLR1 protein is bound to a solid support. In some embodiments,the solid support is a microtiter plate.

In some embodiments, the antibody, antigen-binding fragment thereof, orpolypeptide used to detect FOLR1 protein comprises a detection agent. Insome embodiments, the detection agent is a chromogenic detection agent,a fluorogenic detection agent, an enzymatic detection agent, or anelectrochemiluminescent detection agent. In some embodiments, thedetection agent is horseradish peroxidase (HRP).

In some embodiments, the FOLR1 protein levels are determined using anenzyme linked immunosorbent assay (ELISA). In some embodiments, theELISA is a sandwich ELISA.

In some embodiments, the active agent comprises the FOLR1 antibodyhuMov19. In some embodiments, the huMov19 is conjugated to a cytotoxicagent. In some embodiments, the huMov19 is administered as an antibodymaytansinoid conjugate further comprising the maytansinoid DM4 and thecleavable sulfo-SPDB linker (IMGN853).

The invention also provides an antibody, antigen-binding fragmentthereof, or polypeptide provided herein for use as a diagnostic.

The invention also provides an antibody, antigen-binding fragmentthereof, or polypeptide provided in, e.g., an antibody orantigen-binding-fragment thereof that does not competitively inhibit thebinding to FOLR1 of an active agent comprising an antibody orantigen-binding fragment thereof that modulates FOLR1 activity, for usein the treatment of a FOLR1-mediated disease or disorder with an activeagent comprising an antibody or antigen-binding fragment thereof thatmodulates FOLR1 activity and/or for monitoring therapeutic efficacy of afixed dose of an active agent comprising an antibody or antigen-bindingfragment thereof that modulates FOLR1 activity.

The invention also provides, an antibody, antigen-binding fragmentthereof, or polypeptide provided herein is for use in a method ofdiagnosing (i) a FOLR1-mediated disease or disorder and/or (ii) theresponse to the treatment of a FOLR1-mediated disease or disorder with afixed dose of an active agent comprising an antibody or antigen-bindingfragment thereof that modulates FOLR1 activity and/or (iii) thetherapeutic efficacy of a treatment with a fixed dose of an active agentcomprising an antibody or antigen-binding fragment thereof thatmodulates FOLR1 activity. In some embodiments, the antibody,antigen-binding fragment thereof, or polypeptide is for use in a methodfor diagnosing cancer in a patient suffering therefrom. In someembodiments, the cancer is associated with elevated levels of FOLR1. Insome embodiments, the antibody, antigen-binding fragment thereof, orpolypeptide comprises a detection agent. In some embodiments, thedetection agent is a chromogenic detection agent, a fluorogenicdetection agent, an enzymatic detection agent, or anelectrochemiluminescent detection agent.

The invention also provides methods wherein the FOLR-1 mediated diseaseis cancer, wherein the active agent comprises IMGN853, and wherein theshed FOLR1 protein level is measured using an ELISA assay using at leasttwo anti-FOLR1 antibodies that do not competitively inhibit the bindingof the active agent to FOLR1, wherein each of the at least twoanti-FOLR1 comprise amino acid sequences selected from the groupconsisting of: (a) SEQ ID NOs: 1, 2, and 3 and SEQ ID NOs: 13, 14, and15; (b) SEQ ID NOs: 4, 5, and 6 and SEQ ID NOs: 16, 17, and 18; (c) SEQID NOs: 7, 8, and 9 and SEQ ID NOs: 19, 20, and 21; and (d) SEQ ID NOs:10, 11, and 12 and SEQ ID NOs: 22, 23, and 24.

The invention also provides methods wherein the FOLR-1 mediated diseaseis cancer, wherein the active agent comprises IMGN853, wherein theanti-FOLR1 antibody that does not competitively inhibit the binding ofthe active agent to FOLR1 comprises the amino acid sequences (a) SEQ IDNOs: 1, 2, and 3 and SEQ ID NOs: 13, 14, and 15; (b) SEQ ID NOs: 4, 5,and 6 and SEQ ID NOs: 16, 17, and 18; (c) SEQ ID NOs: 7, 8, and 9 andSEQ ID NOs: 19, 20, and 21; or (d) SEQ ID NOs: 10, 11, and 12 and SEQ IDNOs: 22, 23, and 24; and wherein the FOLR1 protein is detected bycytometry.

In some embodiments of the methods, the cancer is ovarian cancer. Insome embodiments, the ovarian cancer is platinum resistant or platinumrefractory. In some embodiments, the cancer is NSCLC. In someembodiments, the cancer is endometrial cancer.

The invention also provides active agents wherein the FOLR-1 mediateddisease is cancer, wherein the active agent comprises IMGN853, andwherein the shed FOLR1 protein level is measured using an ELISA assayusing at least two anti-FOLR1 antibodies that do not competitivelyinhibit the binding of the active agent to FOLR1, wherein each of the atleast two anti-FOLR1 comprise amino acid sequences selected from thegroup consisting of: (a) SEQ ID NOs: 1, 2, and 3 and SEQ ID NOs: 13, 14,and 15; (b) SEQ ID NOs: 4, 5, and 6 and SEQ ID NOs: 16, 17, and 18; (c)SEQ ID NOs: 7, 8, and 9 and SEQ ID NOs: 19, 20, and 21; and (d) SEQ IDNOs: 10, 11, and 12 and SEQ ID NOs: 22, 23, and 24.

The invention also provides active agents wherein the FOLR-1 mediateddisease is cancer, wherein the active agent comprises IMGN853, andwherein the shed FOLR1 protein level is measured using an ELISA assayusing at least two anti-FOLR1 antibodies that do not competitivelyinhibit the binding of the active agent to FOLR1, wherein each of the atleast two anti-FOLR1 comprise amino acid sequences selected from thegroup consisting of: (a) SEQ ID NOs: 1, 2, and 3 and SEQ ID NOs: 13, 14,and 15; (b) SEQ ID NOs: 4, 5, and 6 and SEQ ID NOs: 16, 17, and 18; (c)SEQ ID NOs: 7, 8, and 9 and SEQ ID NOs: 19, 20, and 21; and (d) SEQ IDNOs: 10, 11, and 12 and SEQ ID NOs: 22, 23, and 24.

In some embodiments of the active agents, the cancer is ovarian cancer.In some embodiments, the ovarian cancer is platinum resistant orplatinum refractory. In some embodiments, the cancer is NSCLC. In someembodiments, the cancer is endometrial cancer.

The invention also provides a method of treating cancer comprisingadministering an active agent comprising an antibody or antigen-bindingfragment thereof that modulates FOLR1 activity to a patient withelevated shed FOLR1 protein levels relative to a reference FOLR1 proteinlevel, wherein the patient's FOLR1 protein levels were measured using anantibody, antigen-binding fragment, or polypeptide provided herein.

The invention also provides a method of treating cancer comprisingadministering an active agent comprising an antibody or antigen-bindingfragment thereof that modulates FOLR1 activity to a patient withelevated FOLR1 protein levels on circulating tumor cells relative to areference FOLR1 protein level, wherein the patient's FOLR1 proteinlevels were measured using an antibody, antigen-binding fragment, orpolypeptide provided herein. In some embodiments, the active agentcomprises IMGN853. In some embodiments, the cancer is ovarian cancer. Insome embodiments, the ovarian cancer is platinum resistant or platinumrefractory. In some embodiments, the cancer is NSCLC. In someembodiments, the cancer is endometrial cancer.

The invention also provides the use of an antibody, antigen-bindingfragment thereof, or polypeptide of provided herein for the measurementof FOLR1 protein level in a sample in vitro.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1. Schematic representation of FOLR1 shed antigen assay.

FIG. 2. (A) Schematic representation of Mov19 competition ELISA assay.(B) Determination of binding affinity of muFR1-13 by sandwich ELISAusing Mov19.

FIG. 3. (A) Schematic representation of direct binding competition ELISAto determine non-competing FOLR1 binding epitopes. (B) Log transformedgraph of competition ELISA results to screen for binding interference ofanti-FOLR1 antibodies with Mov19.

FIG. 4. Log transformed graph of competition ELISA results to screen forbinding interference of anti-FOLR1 antibodies with muFR1-13.

FIG. 5. Binding affinity of anti-FOLR1 antibodies by sandwich ELISA.

FIG. 6. Binding affinity of FR1-13 by both (A) flow cytometry and (B)sandwich ELISA.

FIG. 7. Log transformed graph of results for antibody binding to FOLR2and FOLR3 by sandwich ELISA.

FIG. 8. Effect of pre-bound folic acid to FOLR1 on the detection of shedFOLR1 antigen using FR1-9 and FR1-13.

FIG. 9. Analysis of human ascites samples for the presence of FOLR1 andthe presence of interfering assay proteins.

FIG. 10. Analysis of normal human pooled plasma samples for the presenceof FOLR1 and the presence of interfering assay proteins.

FIG. 11. Determination of FOLR1 concentration in human ovarian patientplasma samples using FOLR1 sandwich ELISA.

FIG. 12. Schematic representation for interpolating the amount of FOLR1in a patient sample based on a 4PL sigmoidal dose response curve fit ofserially-diluted purified FOLR1-Fc fusion protein standard.

FIG. 13. Titration of anti-FOLR1 antibodies using cell lines with arange of FOLR1 expression levels. For each cell line and dilution,triplicate staining was performed. Mean Fluorescence Intensity (MFI) wasmeasured for FRA expression and averaged and are shown in the table(error represents the SEM).

FIG. 14. Histograms showing FOLR1 expression in cell lines using optimaldilutions of anti-FOLR1 antibodies.

FIG. 15. Graph showing competition between anti-FOLR1 antibodies andIMGN853.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a novel method of detecting shed humanfolate receptor 1 (FOLR1) or FOLR1 on circulating tumor cells in apatient sample. The FOLR1 can be detected using antibodies that do notcompetitively inhibit the binding of an anti-FOLR1 active agent (e.g.,an active agent comprising the antibody huMov19) to FOLR1. Antibodiesthat do not competitively inhibit the binding of an anti-FOLR1 activeagent are especially useful in detecting FOLR1 (e.g., shed FOLR1 orFOLR1 on circulating tumor cells) in samples from patients who have beentreated with the anti-FOLR1 active agent. Shed FOLR1 or FOLR1 oncirculating tumor cells can be used to monitor or determine therapeuticefficacy, or the likelihood of response to the treatment of cancerscharacterized by the overexpression of FOLR1. Novel FOLR1-bindingpolypeptides, such as antibodies, that are useful in the shed FOLR1detection methods as well as additional FOLR1 detection methods (e.g.,IHC for membrane bound and cell associated FOLR1 and CTC assays) arealso disclosed. Related polypeptides and polynucleotides, compositionscomprising the FOLR1-binding agents, and methods of making theFOLR1-binding agents are also provided. In addition, methods providedherein can be used for patient stratification.

I. Definitions

To facilitate an understanding of the present invention, a number ofterms and phrases are defined below.

The terms “human folate receptor 1,” “FOLR1” or “folate receptor alpha(FR-α),” as used herein, refer to any native human FOLR1, unlessotherwise indicated. Thus, all of these terms can refer to either aprotein or nucleic acid sequence as indicated herein. The term “FOLR1”encompasses “full-length,” unprocessed FOLR1 as well as any form ofFOLR1 that results from processing within the cell. The term alsoencompasses naturally occurring variants of FOLR1, e.g., splice variants(except those variants that encompass FOLR2, FOLR3, or FOLR4), allelicvariants and isoforms. The FOLR1 polypeptides described herein can beisolated from a variety of sources, such as from human tissue types orfrom another source, or prepared by recombinant or synthetic methods.Examples of FOLR1 sequences include, but are not limited to NCBIreference numbers P15328, NP_001092242.1, AAX29268.1, AAX37119.1,NP_057937.1, and NP_057936.1. The human FOLR1 sequence is a follows:

(SEQ ID NO: 49) MAQRMTTQLLLLLVWVAVVGEAQTRIAWARTELLNVCMNAKHHKEKPGPEDKLHEQCRPWRKNACCSTNTSQEAHKDVSYLYRFNWNHCGEMAPACKRHFIQDTCLYECSPNLGPWIQQVDQSWRKERVLNVPLCKEDCEQWWEDCRTSYTCKSNWHKGWNWTSGFNKCAVGAACQPFHFYFPTPTVLCNEIWTHSYKVSNYSRGSGRCIQMWFDPAQGNPNEEVARFYAAAMSGAGPWAAWPFLLSLALMLLWLLS.

The terms “shed antigen” and “shed FOLR1” are used interchangeablyherein. These terms refer to a FOLR1 protein that is soluble and that isnot cell associated. In some embodiments it includes the extracellulardomain (ECD) and the glycosylphosphatidyl inositol (GPI) linker. In oneembodiment, the shed FOLR1 includes only the ECD. FOLR1 includes asignal peptide (amino acids 1-24) the FOLR1 protein chain (amino acids25-233 or 234) and a propeptide which can be cleaved (amino acids 235 to257). Shed FOLR can include amino acids 1 to 257, 1 to 233, 1 to 234, 25to 233, 25 to 234 or any other fragments thereof. In some embodimentsthe signal sequence is cleaved. In other embodiments the ECD and the GPIportion can be embedded in a membrane (e.g., a soluble lipid raft). Inone embodiment, the shed FOLR1 can include amino acids 1-233 or afragment thereof.

The term “antibody” means an immunoglobulin molecule that recognizes andspecifically binds to a target, such as a protein, polypeptide, peptide,carbohydrate, polynucleotide, lipid, or combinations of the foregoingthrough at least one antigen recognition site within the variable regionof the immunoglobulin molecule. As used herein, the term “antibody”encompasses intact polyclonal antibodies, intact monoclonal antibodies,antibody fragments (such as Fab, Fab′, F(ab′)2, and Fv fragments),single chain Fv (scFv) mutants, multispecific antibodies such asbispecific antibodies, chimeric antibodies, humanized antibodies, humanantibodies, fusion proteins comprising an antigen determination portionof an antibody, and any other modified immunoglobulin moleculecomprising an antigen recognition site so long as the antibodies exhibitthe desired biological activity. An antibody can be of any of the fivemajor classes of immunoglobulins: IgA, IgD, IgE, IgG, and IgM, orsubclasses (isotypes) thereof (e.g., IgG1, IgG2, IgG3, IgG4, IgA1 andIgA2), based on the identity of their heavy-chain constant domainsreferred to as alpha, delta, epsilon, gamma, and mu, respectively. Thedifferent classes of immunoglobulins have different and well knownsubunit structures and three-dimensional configurations. Antibodies canbe naked or conjugated to other molecules such as toxins, radioisotopes,etc.

In some embodiments, an antibody is a non-naturally occurring antibody.In some embodiments, and antibody is purified from natural components.In some embodiments, an antibody is recombinant produced. In someembodiments, an antibody is produced by a hybridoma.

A “blocking” antibody or an “antagonist” antibody is one which inhibitsor reduces biological activity of the antigen it binds, such as FOLR1.In a certain embodiment, blocking antibodies or antagonist antibodiessubstantially or completely inhibit the biological activity of theantigen. Desirably, the biological activity is reduced by 10%, 20%, 30%,50%, 70%, 80%, 90%, 95%, or even 100%.

The term “anti-FOLR1 antibody” or “an antibody that binds to FOLR1”refers to an antibody that is capable of binding FOLR1 with sufficientaffinity such that the antibody is useful as a diagnostic and/ortherapeutic agent in targeting FOLR1. The extent of binding of ananti-FOLR1 antibody to an unrelated, non-FOLR1 protein is less thanabout 10% of the binding of the antibody to FOLR1 as measured, e.g., bya radioimmunoassay (RIA). In certain embodiments, an antibody that bindsto FOLR1 has a dissociation constant (Kd) of ≦1 μM, ≦100 nM, ≦10 nM, ≦1nM, or ≦0.1 nM. In one embodiment, the anti-FOLR1 antibody does not bindFOLR2, FOLR3, FOLR4, or folic acid.

The term “antibody fragment” refers to a portion of an intact antibodyand refers to the antigenic determining variable regions of an intactantibody. Examples of antibody fragments include, but are not limitedto, Fab, Fab′, F(ab′)2, and Fv fragments, linear antibodies, singlechain antibodies, and multispecific antibodies formed from antibodyfragments. The term “monoclonal antibody” as used herein refers to anantibody obtained from a population of substantially homogeneousantibodies, i.e., the individual antibodies comprising the populationare identical except for possible mutations, e.g., naturally occurringmutations, that may be present in minor amounts. Thus, the modifier“monoclonal” indicates the character of the antibody as not being amixture of discrete antibodies. In certain embodiments, such amonoclonal antibody typically includes an antibody comprising apolypeptide sequence that binds a target, wherein the target-bindingpolypeptide sequence was obtained by a process that includes theselection of a single target binding polypeptide sequence from aplurality of polypeptide sequences. For example, the selection processcan be the selection of a unique clone from a plurality of clones, suchas a pool of hybridoma clones, phage clones, or recombinant DNA clones.It should be understood that a selected target binding sequence can befurther altered, for example, to improve affinity for the target, tohumanize the target binding sequence, to improve its production in cellculture, to reduce its immunogenicity in vivo, to create a multispecificantibody, etc., and that an antibody comprising the altered targetbinding sequence is also a monoclonal antibody of this invention. Incontrast to polyclonal antibody preparations, which typically includedifferent antibodies directed against different determinants (epitopes),each monoclonal antibody of a monoclonal antibody preparation isdirected against a single determinant on an antigen. In addition totheir specificity, monoclonal antibody preparations are advantageous inthat they are typically uncontaminated by other immunoglobulins.

The modifier “monoclonal” indicates the character of the antibody asbeing obtained from a substantially homogeneous population ofantibodies, and is not to be construed as requiring production of theantibody by any particular method. For example, the monoclonalantibodies to be used in accordance with the present invention may bemade by a variety of techniques, including, for example, the hybridomamethod (e.g., Kohler and Milstein, Nature, 256:495-97 (1975); Hongo etal., Hybridoma, 14 (3): 253-260 (1995), Harlow et al., Antibodies: ALaboratory Manual, (Cold Spring Harbor Laboratory Press, 2nd ed. 1988);Hammerling et al., in: Monoclonal Antibodies and T-C ell Hybridomas563-681 (Elsevier, N. Y., 1981)), recombinant DNA methods (see, e.g.,U.S. Pat. No. 4,816,567), phage-display technologies (see, e.g.,Clackson et al., Nature, 352: 624-628 (1991); Marks et al., J. Mol.Biol. 222: 581-597 (1992); Sidhu et al., J. Mol. Biol. 338(2): 299-310(2004); Lee et al., J. Mol. Biol. 340(5): 1073-1093 (2004); Fellouse,Proc. Natl. Acad. Sci. USA 101(34): 12467-12472 (2004); and Lee et al.,J. Immunol. Methods 284(1-2): 119-132 (2004), and technologies forproducing human or human-like antibodies in animals that have parts orall of the human immunoglobulin loci or genes encoding humanimmunoglobulin sequences (see, e.g., WO 1998/24893; WO 1996/34096; WO1996/33735; WO 1991/10741; Jakobovits et al., Proc. Natl. Acad. Sci. USA90: 2551 (1993); Jakobovits et al., Nature 362: 255-258 (1993);Bruggemann et al., Year in Immunol. 7:33 (1993); U.S. Pat. Nos.5,545,807; 5,545,806; 5,569,825; 5,625,126; 5,633,425; and 5,661,016;Marks et al., Bio/Technology 10: 779-783 (1992); Lonberg et al., Nature368: 856-859 (1994); Morrison, Nature 368: 812-813 (1994); Fishwild etal., Nature Biotechnol. 14: 845-851 (1996); Neuberger, NatureBiotechnol. 14: 826 (1996); and Lonberg and Huszar, Intern. Rev.Immunol. 13: 65-93 (1995).

The term “humanized antibody” refers to forms of non-human (e.g.,murine) antibodies that are specific immunoglobulin chains, chimericimmunoglobulins, or fragments thereof that contain minimal non-human(e.g., murine) sequences. Typically, humanized antibodies are humanimmunoglobulins in which residues from the complementary determiningregion (CDR) are replaced by residues from the CDR of a non-humanspecies (e.g., mouse, rat, rabbit, hamster) that have the desiredspecificity, affinity, and capability (Jones et al., 1986, Nature,321:522-525; Riechmann et al., 1988, Nature, 332:323-327; Verhoeyen etal., 1988, Science, 239:1534-1536). In some instances, the Fv frameworkregion (FR) residues of a human immunoglobulin are replaced with thecorresponding residues in an antibody from a non-human species that hasthe desired specificity, affinity, and capability. The humanizedantibody can be further modified by the substitution of additionalresidues either in the Fv framework region and/or within the replacednon-human residues to refine and optimize antibody specificity,affinity, and/or capability. In general, the humanized antibody willcomprise substantially all of at least one, and typically two or three,variable domains containing all or substantially all of the CDR regionsthat correspond to the non-human immunoglobulin whereas all orsubstantially all of the FR regions are those of a human immunoglobulinconsensus sequence. The humanized antibody can also comprise at least aportion of an immunoglobulin constant region or domain (Fc), typicallythat of a human immunoglobulin. Examples of methods used to generatehumanized antibodies are described in U.S. Pat. Nos. 5,225,539 or5,639,641. “Resurfacing” antibodies generally involves identification ofthe variable region framework surface residues in both the light andheavy chains and replacing them with human equivalents. Methods ofresurfacing antibodies have been provided, for example in Roguska etal., Proc. Natl. Acad. Sci., USA, 91(3):969-973 (1994) and Roguska etal., Protein Eng. 9(10):895-904 (1996), which are incorporated in theirentirety herein by reference.

A “variable region” of an antibody refers to the variable region of theantibody light chain or the variable region of the antibody heavy chain,either alone or in combination. The variable regions of the heavy andlight chain each consist of four framework regions (FR) connected bythree complementarity determining regions (CDRs) also known ashypervariable regions. The CDRs in each chain are held together in closeproximity by the FRs and, with the CDRs from the other chain, contributeto the formation of the antigen-binding site of antibodies. There are atleast two techniques for determining CDRs: (1) an approach based oncross-species sequence variability (i.e., Kabat et al. Sequences ofProteins of Immunological Interest, (5th ed., 1991, National Institutesof Health, Bethesda Md.)); and (2) an approach based on crystallographicstudies of antigen-antibody complexes (Al-lazikani et al (1997) J.Molec. Biol. 273:927-948)). In addition, combinations of these twoapproaches are sometimes used in the art to determine CDRs.

The Kabat numbering system is generally used when referring to a residuein the variable domain (approximately residues 1-107 of the light chainand residues 1-113 of the heavy chain) (e.g., Kabat et al., Sequences ofImmunological Interest. 5th Ed. Public Health Service, NationalInstitutes of Health, Bethesda, Md. (1991)).

The amino acid position numbering as in Kabat, refers to the numberingsystem used for heavy chain variable domains or light chain variabledomains of the compilation of antibodies in Kabat et al., Sequences ofProteins of Immunological Interest, 5th Ed. Public Health Service,National Institutes of Health, Bethesda, Md. (1991). Using thisnumbering system, the actual linear amino acid sequence can containfewer or additional amino acids corresponding to a shortening of, orinsertion into, a FR or CDR of the variable domain. For example, a heavychain variable domain can include a single amino acid insert (residue52a according to Kabat) after residue 52 of H2 and inserted residues(e.g., residues 82a, 82b, and 82c, etc. according to Kabat) after heavychain FR residue 82. The Kabat numbering of residues can be determinedfor a given antibody by alignment at regions of homology of the sequenceof the antibody with a “standard” Kabat numbered sequence. Chothiarefers instead to the location of the structural loops (Chothia and LeskJ. Mol. Biol. 196:901-917 (1987)). The end of the Chothia CDR-H1 loopwhen numbered using the Kabat numbering convention varies between H32and H34 depending on the length of the loop (this is because the Kabatnumbering scheme places the insertions at H35A and H35B; if neither 35Anor 35B is present, the loop ends at 32; if only 35A is present, theloop ends at 33; if both 35A and 35B are present, the loop ends at 34).The AbM hypervariable regions represent a compromise between the KabatCDRs and Chothia structural loops, and are used by Oxford Molecular'sAbM antibody modeling software.

Loop Kabat AbM Chothia L1 L24-L34 L24-L34 L24-L34 L2 L50-L56 L50-L56L50-L56 L3 L89-L97 L89-L97 L89-L97 H1 H31-H35B H26-H35B H26-H32..34(Kabat Numbering) H1 H31-H35 H26-H35 H26-H32 (Chothia Numbering) H2H50-H65 H50-H58 H52-H56 H3 H95-H102 H95-H102 H95-H102

The term “human antibody” means an antibody produced by a human or anantibody having an amino acid sequence corresponding to an antibodyproduced by a human made using any technique known in the art. Thisdefinition of a human antibody includes intact or full-lengthantibodies, fragments thereof, and/or antibodies comprising at least onehuman heavy and/or light chain polypeptide such as, for example, anantibody comprising murine light chain and human heavy chainpolypeptides.

The term “chimeric antibodies” refers to antibodies wherein the aminoacid sequence of the immunoglobulin molecule is derived from two or morespecies. Typically, the variable region of both light and heavy chainscorresponds to the variable region of antibodies derived from onespecies of mammals (e.g., mouse, rat, rabbit, etc.) with the desiredspecificity, affinity, and capability while the constant regions arehomologous to the sequences in antibodies derived from another (usuallyhuman) to avoid eliciting an immune response in that species.

The term “epitope” or “antigenic determinant” are used interchangeablyherein and refer to that portion of an antigen capable of beingrecognized and specifically bound by a particular antibody. When theantigen is a polypeptide, epitopes can be formed both from contiguousamino acids and noncontiguous amino acids juxtaposed by tertiary foldingof a protein. Epitopes formed from contiguous amino acids are typicallyretained upon protein denaturing, whereas epitopes formed by tertiaryfolding are typically lost upon protein denaturing. An epitope typicallyincludes at least 3, and more usually, at least 5 or 8-10 amino acids ina unique spatial conformation.

“Binding affinity” generally refers to the strength of the sum total ofnoncovalent interactions between a single binding site of a molecule(e.g., an antibody) and its binding partner (e.g., an antigen). Unlessindicated otherwise, as used herein, “binding affinity” refers tointrinsic binding affinity which reflects a 1:1 interaction betweenmembers of a binding pair (e.g., antibody and antigen). The affinity ofa molecule X for its partner Y can generally be represented by thedissociation constant (Kd). Affinity can be measured by common methodsknown in the art, including those described herein. Low-affinityantibodies generally bind antigen slowly and tend to dissociate readily,whereas high-affinity antibodies generally bind antigen faster and tendto remain bound longer. A variety of methods of measuring bindingaffinity are known in the art, any of which can be used for purposes ofthe present invention. Specific illustrative embodiments are describedherein.

“Or better” when used herein to refer to binding affinity refers to astronger binding between a molecule and its binding partner. “Or better”when used herein refers to a stronger binding, represented by a smallernumerical Kd value. For example, an antibody which has an affinity foran antigen of “0.6 nM or better,” the antibody's affinity for theantigen is <0.6 nM, i.e., 0.59 nM, 0.58 nM, 0.57 nM etc. or any valueless than 0.6 nM. In one embodiment, the antibody's affinity asdetermined by a Kd will be between about 10⁻³ to about 10⁻¹² M, betweenabout 10⁻⁶ to about 10⁻¹¹ M, between about 10⁻⁶ to about 10⁻¹⁰ M,between about 10⁻⁶ to about 10⁻⁹ M, between about 10⁻⁶ to about 10⁻⁸ M,or between about 10⁻⁶ to about 10⁻⁷ M.

The phrase “substantially similar,” or “substantially the same,” as usedherein, denotes a sufficiently high degree of similarity between twonumeric values (generally one associated with an antibody of theinvention and the other associated with a reference/comparator antibody)such that one of skill in the art would consider the difference betweenthe two values to be of little or no biological and/or statisticalsignificance within the context of the biological characteristicsmeasured by said values (e.g., Kd values). The difference between saidtwo values is less than about 50%, less than about 40%, less than about30%, less than about 20%, or less than about 10% as a function of thevalue for the reference/comparator antibody.

A polypeptide, antibody, polynucleotide, vector, cell, or compositionwhich is “isolated” is a polypeptide, antibody, polynucleotide, vector,cell, or composition which is in a form not found in nature. Isolatedpolypeptides, antibodies, polynucleotides, vectors, cells orcompositions include those which have been purified to a degree thatthey are no longer in a form in which they are found in nature. In someembodiments, an antibody, polynucleotide, vector, cell, or compositionwhich is isolated is substantially pure.

As used herein, “substantially pure” refers to material which is atleast 50% pure (i.e., free from contaminants), at least 90% pure, atleast 95% pure, at least 98% pure, or at least 99% pure.

The term “increased expression” of FOLR1 refers to a sample whichcontains elevated levels of FOLR1 expression as compared to a referencesample, a reference FOLR1 level, or a previous FOLR1 level detected fromthe same subject. Thus, for example, “increased FOLR1 protein levels” ina patient sample can have FOLR1 protein levels that are higher than theFOLR1 protein levels in a non-cancerous reference sample. “IncreasedFOLR1 protein levels” in a patient sample can also, for example, haveFOLR1 protein levels that are equal to the FOLR1 protein levels in acancerous sample. In some embodiments, “increased FOLR1 protein levels”are detected wherein a patient's FOLR1 protein level is at least about5%, at least about 10%, at least about 15%, at least about 20%, or atleast about 25%, at least about 30%, or at least about 50% more than,for example, a previous FOLR1 level detected from the same subject. Incirculating tumor cell assays, “increased FOLR1 protein levels” canrefer to samples in which FOLR1 is detected on a greater percentage ofcells or samples in which FOLR1 is detected in higher levels on thecells. Thus, in some embodiments, “increased FOLR1 protein levels” aredetected in CTC assays where at least about 5%, at least about 10%, atleast about 15%, at least about 20%, or at least about 25%, at leastabout 30%, or at least about 50% more cells show FOLR1 expression. Inaddition, in some embodiments, “increased FOLR1 protein levels” aredetected in CTC assays where at least about 5%, at least about 10%, atleast about 15%, at least about 20%, or at least about 25%, at leastabout 30%, or at least about 50% more FOLR1 is detected on cells.

A “reference sample” can be used to correlate and compare the resultsobtained in the methods of the invention from a test sample. Referencesamples can be cells (e.g., cell lines, cell pellets), bodily fluids, ortissue. The FOLR1 levels in the “reference sample” may be an absolute orrelative amount, a range of amount, a minimum and/or maximum amount, amean amount, and/or a median amount of FOLR1. A “reference sample” canalso serve as a baseline of FOLR1 expression to which the test sample iscompared. The “reference sample” can include a prior sample or baselinesample from the same patient, a normal reference, or a reference from arelevant patient population. Generally, FOLR1 levels are expressed asvalues in a standard curve. A standard curve is a quantitative method ofplotting assay data to determine the concentration of FOLR1 in a sample.In one embodiment, reference sample is an antigen standard comprisingpurified FOLR1 or FOLR1-Fc. The diagnostic methods of the inventioninvolve a comparison between expression levels of FOLR1 in a test sampleand a “reference value” or “reference level.” In some embodiments, thereference value is the expression level of the FOLR1 in a referencesample. A reference value may be a predetermined value and may also bedetermined from reference samples (e.g., control biological samples)tested in parallel with the test samples. A reference value can be asingle cut-off value, such as a median or mean or a range of values,such as a confidence interval. Reference values can be established forvarious subgroups of individuals, such as individuals predisposed tocancer, individuals having early or late stage cancer, male and/orfemale individuals, or individuals undergoing cancer therapy. Examplesof normal reference samples or values and positive reference samples orvalues are described herein.

The term “primary antibody” herein refers to an antibody that bindsspecifically to the target protein antigen in a sample. A primaryantibody is generally the first antibody used in an ELISA assay. In oneembodiment, the primary antibody is the only antibody used in an IHCprocedure. The term “secondary antibody” herein refers to an antibodythat binds specifically to a primary antibody, thereby forming a bridgebetween the primary antibody and a subsequent reagent, if any. Thesecondary antibody is generally the second antibody used in animmunohistochemical procedure.

As used herein, “immunohistochemistry” refers to histochemical andimmunologic methods used to analyze, for example, cells or tissues.Thus, the terms “immunohistochemistry,” “immunocytochemistry,” and“immunochemistry” are used interchangeably.

A “sample” or “biological sample” of the present invention is ofbiological origin, in specific embodiments, such as from eukaryoticorganisms. In preferred embodiments, the sample is a human sample, butanimal samples may also be used in the practice of the invention.Non-limiting sources of a sample for use in the present inventioninclude solid tissue, biopsy aspirates, ascites, fluidic extracts,blood, plasma, serum, spinal fluid, lymph fluid, the external sectionsof the skin, respiratory, intestinal, and genitourinary tracts, tears,saliva, milk, tumors, organs, cell cultures and/or cell cultureconstituents, for example. The present invention is particularly usefulfor cancer samples which generally comprise bodily fluids such asascites, where the amount of available material is small. The method canbe used to examine an aspect of expression of FOLR1 or a state of asample, including, but not limited to, comparing different types ofcells or tissues, comparing different developmental stages, anddetecting or determining the presence and/or type of disease orabnormality.

As used herein, the term “capture reagent” refers to a reagent capableof binding and capturing a target molecule in a sample such that undersuitable condition, the capture reagent-target molecule complex can beseparated from the rest of the sample. In one embodiment, the capturereagent is immobilized. In one embodiment, the capture reagent in asandwich immunoassay is an antibody or a mixture of different antibodiesagainst a target antigen.

As used herein, the term “detectable antibody” refers to an antibodythat is capable of being detected either directly through a labelamplified by a detection means, or indirectly through, e.g., anotherantibody that is labeled. For direct labeling, the antibody is typicallyconjugated to a moiety that is detectable by some means. In oneembodiment, the detectable antibody is a biotinylated antibody.

The word “label” when used herein refers to a detectable compound orcomposition which is conjugated directly or indirectly to the antibodyso as to generate a “labeled” antibody. The label can be detectable byitself (e.g., radioisotope labels or fluorescent labels) or, in the caseof an enzymatic label, can catalyze chemical alteration of a substratecompound or composition which is detectable.

As used herein, the term “detection means” refers to a moiety ortechnique used to detect the presence of the detectable antibody in theELISA herein and includes detection agents that amplify the immobilizedlabel such as label captured onto a microtiter plate. In one embodiment,the detection means is a fluorimetric detection agent such as avidin orstreptavidin.

Commonly a “sandwich ELISA” employs the following steps: (1) microtiterplate is coated with a capture antibody; (2) sample is added, and anyantigen present binds to capture antibody; (3) detecting antibody isadded and binds to antigen; (4) enzyme-linked secondary antibody isadded and binds to detecting antibody; and (5) substrate is added and isconverted by enzyme to detectable form.

By “correlate” or “correlating” is meant comparing, in any way, theperformance and/or results of a first analysis with the performanceand/or results of a second analysis. For example, one may use theresults of a first analysis in carrying out the second analysis and/orone may use the results of a first analysis to determine whether asecond analysis should be performed and/or one may compare the resultsof a first analysis with the results of a second analysis. In oneembodiment, increased expression of FOLR1 correlates with increasedlikelihood of effectiveness of a FOLR1-targeting anti-cancer therapy.

The terms “cancer” and “cancerous” refer to or describe thephysiological condition in mammals in which a population of cells arecharacterized by unregulated cell growth. Examples of cancer include,but are not limited to, carcinoma, lymphoma, blastoma, sarcoma, andleukemia. More particular examples of such cancers include cancers ofendothelial, mesenchymal, or epithelial origin, such as lung cancer(e.g., squamous cell cancer, small-cell lung cancer, non-small cell lungcancer, adenocarcinoma of the lung, mesothelioma, and squamous carcinomaof the lung), cancer of the peritoneum (e.g., primary peritoneal),hepatocellular cancer, gastrointestinal cancer, pancreatic cancer,glioblastoma, cervical cancer, ovarian cancer, liver cancer, bladdercancer, hepatoma, breast cancer, colon cancer, colorectal cancer,endometrial (e.g., endometrial adenocarcinoma) or uterine carcinoma,salivary gland carcinoma, kidney cancer, liver cancer, prostate cancer,vulval cancer, thyroid cancer, hepatic carcinoma, brain cancer (e.g.glioblastoma, tumors of the choroid plexus) and various types of headand neck cancers, and also tumors of blood vessels and fallopian tubes.Cancers also encompass cancers which contain cells having elevated FOLR1expression levels. Such FOLR1-elevated cancers include, but are notlimited to, ovarian, non-small cell lung cancer, uterine, endometrial,pancreatic, renal, lung, and breast cancer.

“Tumor” and “neoplasm” refer to any mass of tissue that result fromexcessive cell growth or proliferation, either benign (noncancerous) ormalignant (cancerous) including pre-cancerous lesions.

The terms “cancer cell,” “tumor cell,” and grammatical equivalents referto the total population of cells derived from a tumor or a pre-cancerouslesion, including both non-tumorigenic cells, which comprise the bulk ofthe tumor cell population, and tumorigenic stem cells (cancer stemcells). As used herein, the term “tumor cell” will be modified by theterm “non-tumorigenic” when referring solely to those tumor cellslacking the capacity to renew and differentiate to distinguish thosetumor cells from cancer stem cells.

The term “subject” refers to any animal (e.g., a mammal), including, butnot limited to humans, non-human primates, rodents, and the like, whichis to be the recipient of a particular treatment. Typically, the terms“subject” and “patient” are used interchangeably herein in reference toa human subject.

The term “pharmaceutical formulation” refers to a preparation which isin such form as to permit the biological activity of the activeingredient to be effective, and which contains no additional componentswhich are unacceptably toxic to a subject to which the formulation wouldbe administered. Such formulation can be sterile.

An “effective amount” of an antibody as disclosed herein is an amountsufficient to carry out a specifically stated purpose. An “effectiveamount” can be determined empirically and in a routine manner, inrelation to the stated purpose.

The term “therapeutically effective amount” or “fixed dose” refers to anamount of an antibody or other drug effective to “treat” a disease ordisorder in a subject or mammal. In the case of cancer, thetherapeutically effective amount of the drug can reduce the number ofcancer cells; reduce the tumor size; inhibit (i.e., slow to some extentand in a certain embodiment, stop) cancer cell infiltration intoperipheral organs; inhibit (i.e., slow to some extent and in a certainembodiment, stop) tumor metastasis; inhibit, to some extent, tumorgrowth; relieve to some extent one or more of the symptoms associatedwith the cancer; and/or result in a favorable response such as increasedprogression-free survival (PFS), disease-free survival (DFS), or overallsurvival (OS), complete response (CR), partial response (PR), or, insome cases, stable disease (SD), a decrease in progressive disease (PD),a reduced time to progression (TTP), a decrease in CA125 in the case ofovarian cancer, or any combination thereof. See the definition herein of“treating.” To the extent the drug can prevent growth and/or killexisting cancer cells, it can be cytostatic and/or cytotoxic. A“prophylactically effective amount” refers to an amount effective, atdosages and for periods of time necessary, to achieve the desiredprophylactic result. Typically but not necessarily, since a prophylacticdose is used in subjects prior to or at an earlier stage of disease, theprophylactically effective amount will be less than the therapeuticallyeffective amount.

PFS, DFS, and OS can be measured by standards set by the National CancerInstitute and the U.S. Food and Drug Administration for the approval ofnew drugs. See Johnson et al, (2003) J. Clin. Oncol. 21(7):1404-1411.

“Progression free survival” (PFS) refers to the time from enrollment todisease progression or death. PFS is generally measured using theKaplan-Meier method and Response Evaluation Criteria in Solid Tumors(RECIST) 1.1 standards. Generally, progression free survival refers tothe situation wherein a patient remains alive, without the cancergetting worse.

“Time to Tumor Progression” (TTP) is defined as the time from enrollmentto disease progression. TTP is generally measured using the RECIST 1.1criteria.

A “complete response” or “complete remission” or “CR” indicates thedisappearance of all signs of tumor or cancer in response to treatment.This does not always mean the cancer has been cured.

A “partial response” or “PR” refers to a decrease in the size or volumeof one or more tumors or lesions, or in the extent of cancer in thebody, in response to treatment.

“Stable disease” refers to disease without progression or relapse. Instable disease there is neither sufficient tumor shrinkage to qualifyfor partial response nor sufficient tumor increase to qualify asprogressive disease.

“Progressive disease” refers to the appearance of one more new lesionsor tumors and/or the unequivocal progression of existing non-targetlesions. Progressive disease can also refer to a tumor growth of morethan 20 percent since treatment began, either due to an increases inmass or in spread of the tumor.

“Disease free survival” (DFS) refers to the length of time during andafter treatment that the patient remains free of disease.

“Overall Survival” (OS) refers to the time from patient enrollment todeath or censored at the date last known alive. OS includes aprolongation in life expectancy as compared to naive or untreatedindividuals or patients. Overall survival refers to the situationwherein a patient remains alive for a defined period of time, such asone year, five years, etc., e.g., from the time of diagnosis ortreatment.

A “decrease in CA125 levels” can be assessed according to theGynecologic Cancer Intergroup (GCIG) guidelines. For example, CA125levels can be measured prior to treatment to establish a baseline CA125level. CA125 levels can be measured one or more times during or aftertreatment, and a reduction in the CA125 levels over time as compared tothe baseline level is considered a decrease in CA125 levels.

Terms such as “treating” or “treatment” or “to treat” or “alleviating”or “to alleviate” refer to both 1) therapeutic measures that cure, slowdown, lessen symptoms of, and/or halt progression of a diagnosedpathologic condition or disorder and 2) prophylactic or preventativemeasures that prevent and/or slow the development of a targetedpathologic condition or disorder. Thus, those in need of treatmentinclude those already with the disorder; those prone to have thedisorder; and those in whom the disorder is to be prevented. In certainembodiments, a subject is successfully “treated” for cancer according tothe methods of the present invention if the patient shows one or more ofthe following: reduction in cachexia, increase in survival time,elongation in time to tumor progression, reduction in tumor mass,reduction in tumor burden and/or a prolongation in time to tumormetastasis, time to tumor recurrence, tumor response, complete response,partial response, stable disease, progressive disease, progression freesurvival (PFS), overall survival (OS), each as measured by standards setby the National Cancer Institute and the U.S. Food and DrugAdministration for the approval of new drugs. See Johnson et al, (2003)J. Clin. Oncol. 21(7):1404-1411.

“Polynucleotide” or “nucleic acid,” as used interchangeably herein,refer to polymers of nucleotides of any length, and include DNA and RNA.The nucleotides can be deoxyribonucleotides, ribonucleotides, modifiednucleotides or bases, and/or their analogs, or any substrate that can beincorporated into a polymer by DNA or RNA polymerase. A polynucleotidecan comprise modified nucleotides, such as methylated nucleotides andtheir analogs. If present, modification to the nucleotide structure canbe imparted before or after assembly of the polymer. The sequence ofnucleotides can be interrupted by non-nucleotide components. Apolynucleotide can be further modified after polymerization, such as byconjugation with a labeling component. Other types of modificationsinclude, for example, “caps,” substitution of one or more of thenaturally occurring nucleotides with an analog, internucleotidemodifications such as, for example, those with uncharged linkages (e.g.,methyl phosphonates, phosphotriesters, phosphoamidates, cabamates, etc.)and with charged linkages (e.g., phosphorothioates, phosphorodithioates,etc.), those containing pendant moieties, such as, for example, proteins(e.g., nucleases, toxins, antibodies, signal peptides, ply-L-lysine,etc.), those with intercalators (e.g., acridine, psoralen, etc.), thosecontaining chelators (e.g., metals, radioactive metals, boron, oxidativemetals, etc.), those containing alkylators, those with modified linkages(e.g., alpha anomeric nucleic acids, etc.), as well as unmodified formsof the polynucleotide(s). Further, any of the hydroxyl groups ordinarilypresent in the sugars can be replaced, for example, by phosphonategroups, phosphate groups, protected by standard protecting groups, oractivated to prepare additional linkages to additional nucleotides, orcan be conjugated to solid supports. The 5′ and 3′ terminal OH can bephosphorylated or substituted with amines or organic capping groupmoieties of from 1 to 20 carbon atoms. Other hydroxyls can also bederivatized to standard protecting groups. Polynucleotides can alsocontain analogous forms of ribose or deoxyribose sugars that aregenerally known in the art, including, for example, 2′-O-methyl-,2′-O-allyl, 2′-fluoro- or 2′-azido-ribose, carbocyclic sugar analogs,alpha-anomeric sugars, epimeric sugars such as arabinose, xyloses orlyxoses, pyranose sugars, furanose sugars, sedoheptuloses, acyclicanalogs and abasic nucleoside analogs such as methyl riboside. One ormore phosphodiester linkages can be replaced by alternative linkinggroups. These alternative linking groups include, but are not limitedto, embodiments wherein phosphate is replaced by P(O)S (“thioate”),P(S)S (“dithioate”), (O)NR₂ (“amidate”), P(O)R, P(O)OR′, CO or CH₂(“formacetal”), in which each R or R′ is independently H or substitutedor unsubstituted alkyl (1-20 C) optionally containing an ether (—O—)linkage, aryl, alkenyl, cycloalkyl, cycloalkenyl or araldyl. Not alllinkages in a polynucleotide need be identical. The precedingdescription applies to all polynucleotides referred to herein, includingRNA and DNA.

The term “vector” means a construct, which is capable of delivering, andexpressing, one or more gene(s) or sequence(s) of interest in a hostcell. Examples of vectors include, but are not limited to, viralvectors, naked DNA or RNA expression vectors, plasmid, cosmid or phagevectors, DNA or RNA expression vectors associated with cationiccondensing agents, DNA or RNA expression vectors encapsulated inliposomes, and certain eukaryotic cells, such as producer cells.

The terms “polypeptide,” “peptide,” and “protein” are usedinterchangeably herein to refer to polymers of amino acids of anylength. The polymer can be linear or branched, it can comprise modifiedamino acids, and it can be interrupted by non-amino acids. The termsalso encompass an amino acid polymer that has been modified naturally orby intervention; for example, disulfide bond formation, glycosylation,lipidation, acetylation, phosphorylation, or any other manipulation ormodification, such as conjugation with a labeling component. Alsoincluded within the definition are, for example, polypeptides containingone or more analogs of an amino acid (including, for example, unnaturalamino acids, etc.), as well as other modifications known in the art. Itis understood that, because the polypeptides of this invention are basedupon antibodies, in certain embodiments, the polypeptides can occur assingle chains or associated chains. In some embodiments, a polypeptide,peptide, or protein is non-naturally occurring. In some embodiments, apolypeptide, peptide, or protein is purified from other naturallyoccurring components. In some embodiments, the polypeptide, peptide, orprotein is recombinantly produced.

The terms “identical” or percent “identity” in the context of two ormore nucleic acids or polypeptides, refer to two or more sequences orsubsequences that are the same or have a specified percentage ofnucleotides or amino acid residues that are the same, when compared andaligned (introducing gaps, if necessary) for maximum correspondence, notconsidering any conservative amino acid substitutions as part of thesequence identity. The percent identity can be measured using sequencecomparison software or algorithms or by visual inspection. Variousalgorithms and software are known in the art that can be used to obtainalignments of amino acid or nucleotide sequences. One such non-limitingexample of a sequence alignment algorithm is the algorithm described inKarlin et al, 1990, Proc. Natl. Acad. Sci., 87:2264-2268, as modified inKarlin et al., 1993, Proc. Natl. Acad. Sci., 90:5873-5877, andincorporated into the NBLAST and XBLAST programs (Altschul et al., 1991,Nucleic Acids Res., 25:3389-3402). In certain embodiments, Gapped BLASTcan be used as described in Altschul et al., 1997, Nucleic Acids Res.25:3389-3402. BLAST-2, WU-BLAST-2 (Altschul et al., 1996, Methods inEnzymology, 266:460-480), ALIGN, ALIGN-2 (Genentech, South SanFrancisco, Calif.) or Megalign (DNASTAR) are additional publiclyavailable software programs that can be used to align sequences. Incertain embodiments, the percent identity between two nucleotidesequences is determined using the GAP program in GCG software (e.g.,using a NWSgapdna.CMP matrix and a gap weight of 40, 50, 60, 70, or 90and a length weight of 1, 2, 3, 4, 5, or 6). In certain alternativeembodiments, the GAP program in the GCG software package, whichincorporates the algorithm of Needleman and Wunsch (J. Mol. Biol.(48):444-453 (1970)) can be used to determine the percent identitybetween two amino acid sequences (e.g., using either a Blossum 62 matrixor a PAM250 matrix, and a gap weight of 16, 14, 12, 10, 8, 6, or 4 and alength weight of 1, 2, 3, 4, 5). Alternatively, in certain embodiments,the percent identity between nucleotide or amino acid sequences isdetermined using the algorithm of Myers and Miller (CABIOS, 4:11-17(1989)). For example, the percent identity can be determined using theALIGN program (version 2.0) and using a PAM120 with residue table, a gaplength penalty of 12 and a gap penalty of 4. Appropriate parameters formaximal alignment by particular alignment software can be determined byone skilled in the art. In certain embodiments, the default parametersof the alignment software are used. In certain embodiments, thepercentage identity “X” of a first amino acid sequence to a secondsequence amino acid is calculated as 100×(Y/Z), where Y is the number ofamino acid residues scored as identical matches in the alignment of thefirst and second sequences (as aligned by visual inspection or aparticular sequence alignment program) and Z is the total number ofresidues in the second sequence. If the length of a first sequence islonger than the second sequence, the percent identity of the firstsequence to the second sequence will be longer than the percent identityof the second sequence to the first sequence.

As a non-limiting example, whether any particular polynucleotide has acertain percentage sequence identity (e.g., is at least 80% identical,at least 85% identical, at least 90% identical, and in some embodiments,at least 95%, 96%, 97%, 98%, or 99% identical) to a reference sequencecan, in certain embodiments, be determined using the Bestfit program(Wisconsin Sequence Analysis Package, Version 8 for Unix, GeneticsComputer Group, University Research Park, 575 Science Drive, Madison,Wis. 53711). Bestfit uses the local homology algorithm of Smith andWaterman, Advances in Applied Mathematics 2: 482 489 (1981), to find thebest segment of homology between two sequences. When using Bestfit orany other sequence alignment program to determine whether a particularsequence is, for instance, 95% identical to a reference sequenceaccording to the present invention, the parameters are set such that thepercentage of identity is calculated over the full length of thereference nucleotide sequence and that gaps in homology of up to 5% ofthe total number of nucleotides in the reference sequence are allowed.

In some embodiments, two nucleic acids or polypeptides of the inventionare substantially identical, meaning they have at least 70%, at least75%, at least 80%, at least 85%, at least 90%, and in some embodimentsat least 95%, 96%, 97%, 98%, 99% nucleotide or amino acid residueidentity, when compared and aligned for maximum correspondence, asmeasured using a sequence comparison algorithm or by visual inspection.In certain embodiments, identity exists over a region of the sequencesthat is at least about 10, about 20, about 40-60 residues in length orany integral value therebetween, or over a longer region than 60-80residues, at least about 90-100 residues, or the sequences aresubstantially identical over the full length of the sequences beingcompared, such as the coding region of a nucleotide sequence forexample.

A “conservative amino acid substitution” is one in which one amino acidresidue is replaced with another amino acid residue having a similarside chain. Families of amino acid residues having similar side chainshave been defined in the art, including basic side chains (e.g., lysine,arginine, histidine), acidic side chains (e.g., aspartic acid, glutamicacid), uncharged polar side chains (e.g., asparagine, glutamine, serine,threonine, tyrosine, cysteine), nonpolar side chains (e.g., glycine,alanine, valine, leucine, isoleucine, proline, phenylalanine,methionine, tryptophan), beta-branched side chains (e.g., threonine,valine, isoleucine) and aromatic side chains (e.g., tyrosine,phenylalanine, tryptophan, histidine). For example, substitution of aphenylalanine for a tyrosine is a conservative substitution. In certainembodiments, conservative substitutions in the sequences of thepolypeptides and antibodies of the invention do not abrogate the bindingof the polypeptide or antibody containing the amino acid sequence, tothe antigen(s), i.e., the FOLR1 to which the polypeptide or antibodybinds. Methods of identifying nucleotide and amino acid conservativesubstitutions which do not eliminate antigen-binding are well-known inthe art (see, e.g., Brummell et al., Biochem. 32: 1180-1 187 (1993);Kobayashi et al. Protein Eng. 12(10):879-884 (1999); and Burks et al.Proc. Natl. Acad. Sci. USA 94:412-417 (1997)).

As used in the present disclosure and claims, the singular forms “a,”“an,” and “the” include plural forms unless the context clearly dictatesotherwise.

It is understood that wherever embodiments are described herein with thelanguage “comprising,” otherwise analogous embodiments described interms of “consisting of” and/or “consisting essentially of” are alsoprovided.

The term “and/or” as used in a phrase such as “A and/or B” herein isintended to include both “A and B,” “A or B,” “A,” and “B.” Likewise,the term “and/or” as used in a phrase such as “A, B, and/or C” isintended to encompass each of the following embodiments: A, B, and C; A,B, or C; A or C; A or B; B or C; A and C; A and B; B and C; A (alone); B(alone); and C (alone).

II. SHED ANTIGEN ASSAY

The antibody maytansinoid conjugate (AMC),IMGN853, comprises theFOLR1-binding monoclonal antibody, huMov 19 (M9346A), conjugated to themaytansinoid, DM4(N(2′)-deacetyl-N2′-(4-mercapto-4-methyl-1-oxopentyl)-maytansine),attached via the cleavable sulfo-SPDB (N-succinimidyl4-(2-pyridyldithio)-2-sulfobutanoate) linker. IMGN853 and huMov19 aredescribed in co-pending US Appl. Pub. No. 2012/0009181, which is hereinincorporated by reference in its entirety. The huMov19 antibody isencoded by the plasmids deposited with the American Type CultureCollection (ATCC) at 10801 University Boulevard Manassas Virinia 20110on Apr. 7, 2010 and having ATCC deposit nos. PTA-10772 and PTA-10773 or10774. The FOLR1 antigen contains a single epitope recognized by Mov19.In one embodiment, the huMov 19 antibody comprises the heavy and lightchains with the following sequences:

SEQ ID NO: 46: huMov19 vHCQVQLVQSGAEVVKPGASVKISCKASGYTFTGYFMNWVKQSPGQSLEWIGRIHPYDGDTFYNQKFQGKATLTVDKSSNTAHMELLSLTSEDFAVYYCTRYDGSRAMDYWGQGTTVTVSS huMov19 vLCv1.00 SEQ ID NO: 47DIVLTQSPLSLAVSLGQPAIISCKASQSVSFAGTSLMHWYHQKPGQQPRLLIYRASNLEAGVPDRFSGSGSKTDFTLNISPVEAEDAATYYC QQSREYPYTFGGGTKLEIKRhuMov19 vLCv1.60 SEQ ID NO: 48DIVLTQSPLSLAVSLGQPAIISCKASQSVSFAGTSLMHWYHQKPGQQPRLLIYRASNLEAGVPDRFSGSGSKTDFTLTISPVEAEDAATYYC QQSREYPYTFGGGTKLEIKR.

In some embodiments, an anti-FOLR1 active agent such as IMGN853modulates FOLR1 activity, e.g. decreases the activity of the FOLR1protein.

IMGN853 is currently in clinical development for various therapeuticindications which include FOLR1 positive ovarian cancer, non-small celllung cancer, endometrioid cancer, renal cancer, and other epithelialmalignancies. Ovarian cancers exhibit the greatest FOLR1 penetrance andare considered the major indications for treatment with IMGN853 (AntonyA C. Ann Rev Nutr 16:501-21 (1996); Yuan Y et al. Hum Pathol40(10):1453-1460 (2009)).

Measuring levels of circulating antigen in patient plasma samples (shedantigen) may help identify patient populations more likely to respond toAMC treatment. High levels of shed antigen have been reported tomarkedly affect the pharmacokinetics of therapeutic antibodies (TolcherA. et al. 20th Symposium on Molecular Targets and Cancer Therapeutics;Oct. 21-24, 2008; Geneva, Switzerland: EORTC-NCI-AACR, p 163, #514;Baselga J, et al. J Clin Oncol 14:737-744 (1996)). It is likely thatshed antigen levels from patient plasma samples will be variabledepending on factors such as antigen target, disease indications, anddisease course. Currently shed antigen levels in disease indications forIMGN853 have been insufficiently examined while correlation with solidtumor expression is limited. While elevation of FOLR1 has been reportedin ovarian adenocarcinomas, data suggests that it is not elevated inother FOLR1+ tumor indications, such as small cell lung carcinoma(Mantovani L T, et al. Eur J Cancer 30A(3):363-9 (1994); Basal E, et al.PLoS ONE 4(7): e6292 (2009)). The present method allows for detection ofthe FOLR1 receptor in the presence of high folic acid. Previous assayshave used Mov19 in the design of the assay. Since IMGN853 contains Mov19and in one embodiment is the targeted therapy of the invention, it isvital that the method detects FOLR1 in the presence or absence of Mov19in embodiments where IMGN853 is administered prior to the detection ofFOLR1. Previous assays that use Mov19 have competitive effects and willdetect significantly less or no FOLR1 in patients receiving IMGN853treatment.

In one embodiment, the present method for detecting FOLR1 in humansourced fluid samples uses a traditional sandwich ELISA format (FIG. 1).In one embodiment, the method uses a capture agent (i.e., antibody,other protein) to FOLR1 attached to a solid support. In one embodiment,the solid support is a microtiter plate. To this, the sample (ascitesfluids, blood, serum, plasma, etc.) is added without dilution, and isdetected by a different detection agent (a different antibody orprotein), which does not interfere with the binding of the first captureagent. The detection agent is then detected through the use of asecondary detection agent (biotin/streptavidin, anti-human secondarymono or polyclonal antibody, etc.) which can bind more than one time tothe first detection agent, thus amplifying the signal of detection. Thesecondary detection agent is then quantified by the use of some othermeans (e.g., TMB/peroxidase, scintillation counting, fluorescent probes,etc.). Additionally, the assay detects FOLR1 and is not negativelyimpacted by the presence of Mov19, IMGN853, other FOLR1 family members,or folic acid.

The assays of the present invention include assays both to selectpatients eligible to receive FOLR1-based therapy and assays to monitorpatient response. Assays for response prediction are run before therapyselection, and levels of shed FOLR1 may impact therapy decisions. Formonitoring patient response, the assay is run at the initiation oftherapy to establish baseline (or predetermined) levels of FOLR1 in thesample. The same sample is then assayed and the levels of FOLR1 comparedto the baseline or predetermined levels. As used herein, the term“predetermined level” refers generally to an assay cutoff value that isused to assess diagnostic results by comparing the assay results againstthe predetermined level, and where the predetermined level already hasbeen linked or associated with various clinical parameters (e.g.,monitoring whether a subject being treated with a drug has achieved anefficacious blood level of the drug, monitoring the response of asubject receiving treatment for cancer with an anti-cancer drug,monitoring the response of a tumor in a subject receiving treatment forsaid tumor, etc.). The predetermined level may be either an absolutevalue or a value normalized by subtracting the value obtained from apatient prior to the initiation of therapy. An example of apredetermined level that can be used is a baseline level obtained fromone or more subjects that may optionally be suffering from one or morediseases or conditions. The comparison (or informational analysis) ofthe level of the assayed biomarker with the baseline or predeterminedlevel can be done by an automated system, such as a software program orintelligence system that is part of, or compatible with, the equipment(e.g., computer platform) on which the assay is carried out.Alternatively, this comparison or informational analysis can be done bya physician. In one embodiment, where the levels remain the same ordecrease, the therapy may be effective and can be continued. Wheresignificant increase over baseline level (or predetermined level)occurs, the patient may not be responding. In another embodiment, anincrease in shed FOLR1 levels may be indicative of increased cell deathand increased release of the shed FOLR1. In this embodiment, an increasein shed FOLR1 is indicative of therapeutic efficacy. Accordingly, insome embodiments, shed FOLR1 is measured and cell death is measured.Assays for measuring cell death are known in the art and include, forexample, detection of M30-antigen (caspase-cleaved cytokeratin), markersof DNA damage such as γ-H2AX, or morphological features of cells such asfragmented and/or condensed DAPI-stained nuclei.

The assays of the present invention can be performed by any proteinassay methods. Protein assay methods useful in the invention are wellknown in the art and include immunoassay methods involving binding of aspecific unlabeled or labeled antibody or protein to the expressedprotein or fragment of FOLR1. Useful immunoassay methods include bothsolution phase assays conducted using any format known in the art, suchas, but not limited to, Biacore, time resolved fluorescence energytransfer (TR-FRET), an ELISA format, (sandwich, forward and reversecompetitive inhibition) or a fluorescence polarization format, and solidphase assays such as immunohistochemistry. The FOLR-1 binding agentsprovided below are particularly useful for these immunoassay methods.

III. FOLR1-binding agents

The present invention provides agents that specifically bind humanFOLR1. These agents are referred to herein as “FOLR1-binding agents.”

The FOLR1-binding agents include FOLR1-binding agents that comprise theheavy and light chain CDR sequences of muFR1-9, muFR1-13, muFR1-53,muFR1-62, and muFR1-64. The CDR sequences muFR1-9, muFR1-13, muFR1-53,and muFR1-62 are described in Tables 1 and 2 below.

TABLE 1 Variable heavy chain CDR amino acid sequences Antibody VH-CDR1VH-CDR2 VH-CDR3 muFR1-9 SFGMH YISSGSSTFYYADTVKG ELTGTFAY (SEQ ID(SEQ ID NO: 2)  (SEQ ID NO: 1)  NO: 3)  muFR1-13 RYSVH MIWSGGNTDYNSVFKSFDGKVSWFAY (SEQ ID (SEQ ID NO: 5)  (SEQ ID NO: 4)  NO: 6)  muFR1-53DYDIS EIYPGSGRTYYNERFKG SYYYGTNSPFAY (SEQ ID (SEQ ID NO: 8)  (SEQ IDNO: 7)  NO: 9)  muFR1-62 TYTMH YINPTSGYNNYNQKFKE GGAYGRRPVDY (SEQ ID(SEQ ID NO: 11) (SEQ ID NO: 10) NO: 12)

TABLE 2 Variable light chain CDR amino acid sequences Antibody VL-CDR1VL-CDR2 VL-CDR3 muFR1-9 RASQSINNNLH YASQSIS QQSNSWPQVT (SEQ ID NO: 13)(SEQ ID (SEQ ID NO: 15) NO: 14) muFR1-13 KASQSVSNDVL YAYNRYS QQDHSSPFT(SEQ ID NO: 16) (SEQ ID (SEQ ID NO: 18) NO: 17) muFR1-53 RASQDISNYLHYTSRLQS QQGNSLPPT (SEQ ID NO: 19) (SEQ ID (SEQ ID NO: 21) NO: 20)muFR1-62 KASQNVGTNVA SASSRYS HQYNSYPYT (SEQ ID NO: 22) (SEQ ID(SEQ ID NO: 24) NO: 23)

The FOLR1 binding molecules can be antibodies or antigen-bindingfragments that specifically bind to FOLR1 that comprise the CDRs ofmuFR1-9, muFR1-13, muFR1-53, muFR1-62, or muFR1-64 with up to four(i.e., 0, 1, 2, 3, or 4) conservative amino acid substitutions per CDR.

Polypeptides can comprise one of the individual variable light chains orvariable heavy chains described herein. Antibodies and polypeptides canalso comprise both a variable light chain and a variable heavy chain.The variable light chain and variable heavy chain sequences of murinemuFR1-9, muFR1-13, muFR1-53, and muFR1-62 antibodies are provided inTables 3 and 4 below.

TABLE 3 Variable heavy chain amino acid sequences AntibodyVH Amino Acid Sequence (SEQ ID NO) muFR1-9HCvarQVQLVESGGGLVQPGGSRKLSCAASGFTFSSFGMH WVRQAPEKGLEWVAYISSGSSTFYYADTVKGRFTISRDNPKNTLFLQMTSLRSEDTAMYYCAKELTGTFA YWGQGTLVTVSA (SEQ ID NO: 25)muFR1-13HCvar QVQLKESGPDLVAPSQSLSITCTVSGFSLSRYSVHWIRQPPGKGLEWLGMIWSGGNTDYNSVFKSRLNIT KDNSKSQVFLKMNSLQTDDTAIYYCATFDGKVSWFAYWGQGTLVTVSA (SEQ ID NO: 26) muFR1-53HCQVQLQQSGPELVRPGASVKMSCKASGYKFTDYDIS WVLQRTGQGLEWIGEIYPGSGRTYYNERFKGKATLTADKSSNTVYMQLSSLTSEDSAVYFCASSYYYGTN SPFAYWGQGTTLTVSS (SEQ ID NO: 27)muFR1-62HC QVQLQQSGAELARPGASVKMSCKASGYTFTTYTMHWVKQRPGQGLEWIAYINPTSGYNNYNQKFKEKATL TADKSSSTAYMQLTSLTSEDSAVYYCASGGAYGRRPVDYWGQGTSVTVSS (SEQ ID NO: 28)

TABLE 4 Variable light chain amino acid sequences AntibodyVL Amino Acid Sequence (SEQ ID NO) muFR1-9LCvarDIVLTQSPATLSVTPGDSVSLSCRASQSINNNLH WYQQKSHESPRLLIKYASQSISGIPSRFSGSGSGTDFTLSINSVETEDFGMYFCQQSNSWPQVTFGAG TKLELKR (SEQ ID NO: 29) muFR1-13LCvarSIVMTQTPKFLLVSTGDRFTITCKASQSVSNDVL WYQQKPGQSPKLLIYYAYNRYSGVPDRFTGSGYGTDFTFTITTVQSEDLAVYFCQQDHSSPFTFGSGT KLEIKR (SEQ ID NO: 30) muFR1-53LCDIQMTQTTSSLSASLGDRVTISCRASQDISNYLH WYQRKPDGTVKLLVYYTSRLQSGVPSRFSGSGSGTDYSLTISNLEQEDIATYFCQQGNSLPPTFGSGT KLEIKR (SEQ ID NO: 31) muFR1-62LCDIVMTQSQKFMSISVGDRVSVTCKASQNVGTNVA WYQQKPGQSPKTLIYSASSRYSGVPDRFTGSGSGTDFTLTISNVQSEDLADYFCHQYNSYPYTFGGGT KLEIKR (SEQ ID NO: 32)

Also provided are polypeptides that comprise: (a) a polypeptide havingat least about 90% sequence identity to SEQ ID NOs:25-28; and/or (b) apolypeptide having at least about 90% sequence identity to SEQ IDNOs:29-32. In certain embodiments, the polypeptide comprises apolypeptide having at least about 95%, at least about 96%, at leastabout 97%, at least about 98%, or at least about 99% sequence identityto SEQ ID NOs:25-32. Thus, in certain embodiments, the polypeptidecomprises (a) a polypeptide having at least about 95% sequence identityto SEQ ID NOs:25-28, and/or (b) a polypeptide having at least about 95%sequence identity to SEQ ID NOs:29-32. In certain embodiments, thepolypeptide comprises (a) a polypeptide having the amino acid sequenceof SEQ ID NOs:25-28; and/or (b) a polypeptide having the amino acidsequence of SEQ ID NOs:29-32. In certain embodiments, the polypeptide isan antibody and/or the polypeptide specifically binds FOLR1. In certainembodiments, the polypeptide is a murine, chimeric, or humanizedantibody that specifically binds FOLR1. In certain embodiments, thepolypeptide having a certain percentage of sequence identity to SEQ IDNOs:25-32 differs from SEQ ID NOs:25-32 by conservative amino acidsubstitutions only.

Polypeptides can comprise one of the individual light chains or heavychains described herein. Antibodies and polypeptides can also compriseboth a light chain and a heavy chain. The light chain and variable chainsequences of murine muFR1-9, muFR1-13, muFR1-53, and muFR1-62 antibodiesare provided in Tables 5 and 6 below.

TABLE 5 Full-length heavy chain amino acid sequencesFull-Length Heavy Chain Antibody Amino Acid Sequence (SEQ ID NO)muFR1-9HC QVQLVESGGGLVQPGGSRKLSCAASGFTFSSFGMHWVRQAPEKGLEWVAYISSGSSTFYYAD TVKGRFTISRDNPKNTLFLQMTSLRSEDTAMYYCAKELTGTFAYWGQGTLVTVSAAKTTPPS VYPLAPGSAAQTNSMVTLGCLVKGYFPEPVTVTWNSGSLSSGVHTFPAVLESDLYTLSSSVT VPSSMRPSETVTCNVAHPASSTKVDKKIVPRDCGCKPCICTVPEVSSVFIFPPKPKDVLTIT LTPKVTCVVVDISKDDPEVQFSWFVDDVEVHTAQTQPREEQFNSTFRSVSELPIMHQDWLNG KEFKCRVNSAAFPAPIEKTISKTKGRPKAPQVYTIPPPKEQMAKDKVSLTCMITDFFPEDIT VEWQWNGQPAENYKNTQPIMNTNGSYFVYSKLNVQKSNWEAGNTFTCSVLHEGLHNHHTEKS LSHSPGK (SEQ ID NO: 33) muFR1-13HCQVQLKESGPDLVAPSQSLSITCTVSGFSLSR YSVHWIRQPPGKGLEWLGMIWSGGNTDYNSVFKSRLNITKDNSKSQVFLKMNSLQTDDTAIY YCATFDGKVSWFAYWGQGTLVTVSAAKTTPPSVYPLAPGCGDTTGSSVTLGCLVKGYFPESV TVTWNSGSLSSSVHTFPALLQSGLYTMSSSVTVPSSTWPSQTVTCSVAHPASSTTVDKKLEP SGPISTINPCPPCKECHKCPAPNLEGGPSVFIFPPNIKDVLMISLTPKVTCVVVDVSEDDPD VQISWFVNNVEVHTAQTQTHREDYNSTIRVVSTLPIQHQDWMSGKEFKCKVNNKDLPSPIER TISKIKGLVRAPQVYILPPPAEQLSRKDVSLTCLVVGFNPGDISVEWTSNGHTEENYKDTAP VLDSDGSYFIYSKLNMKTSKWEKTDSFSCNVRHEGLKNYYLKKTISRSPGK (SEQ ID NO: 34) muFR1-53HCQVQLQQSGPELVRPGASVKMSCKASGYKFTD YDISWVLQRTGQGLEWIGEIYPGSGRTYYNERFKGKATLTADKSSNTVYMQLSSLTSEDSAV YFCASSYYYGTNSPFAYWGQGTTLTVSSAKTTPPSVYPLAPGSAAQTNSMVTLGCLVKGYFP EPVTVTWNSGSLSSGVHTFPAVLESDLYTLSSSVTVPSSMRPSETVTCNVAHPASSTKVDKK IVPRDCGCKPCICTVPEVSSVFIFPPKPKDVLTITLTPKVTCVVVDISKDDPEVQFSWFVDD VEVHTAQTQPREEQFNSTFRSVSELPIMHQDWLNGKEFKCRVNSAAFPAPIEKTISKTKGRP KAPQVYTIPPPKEQMAKDKVSLTCMITDFFPEDITVEWQWNGQPAENYKNTQPIMNTNGSYF VYSKLNVQKSNWEAGNTFTCSVLHEGLHNHHTEKSLSHSPGK (SEQ ID NO: 35) muFR1-62HC QVQLQQSGAELARPGASVKMSCKASGYTFTTYTMHWVKQRPGQGLEWIAYINPTSGYNNYNQ KFKEKATLTADKSSSTAYMQLTSLTSEDSAVYYCASGGAYGRRPVDYWGQGTSVTVSSAKTT PPSVYPLAPGSAAQTNSMVTLGCLVKGYFPEPVTVTWNSGSLSSGVHTFPAVLESDLYTLSS SVTVPSSMRPSETVTCNVAHPASSTKVDKKIVPRDCGCKPCICTVPEVSSVFIFPPKPKDVL TITLTPKVTCVVVDISKDDPEVQFSWFVDDVEVHTAQTQPREEQFNSTFRSVSELPIMHQDW LNGKEFKCRVNSAAFPAPIEKTISKTKGRPKAPQVYTIPPPKEQMAKDKVSLTCMITDFFPE DITVEWQWNGQPAENYKNTQPIMNTNGSYFVYSKLNVQKSNWEAGNTFTCSVLHEGLHNHHT EKSLSHSPGK (SEQ ID NO: 36)

TABLE 6 Full-length light chain amino acid sequencesFull-length Light Chain Antibody Amino Acid Sequence (SEQ ID NO)muFR1-9LC DIVLTQSPATLSVTPGDSVSLSCRASQSINNNLHWYQQKSHESPRLLIKYASQSISGIPSRF SGSGSGTDFTLSINSVETEDFGMYFCQQSNSWPQVTFGAGTKLELKRADAAPTVSIFPPSSE QLTSGGASVVCFLNNFYPKDINVKWKIDGSERQNGVLNSWTDQDSKDSTYSMSSTLTLTKDE YERHNSYTCEATHKTSTSPIVKSFNRNEC(SEQ ID NO: 37) muFR1-13LC SIVMTQTPKFLLVSTGDRFTITCKASQSVSNDVLWYQQKPGQSPKLLIYYAYNRYSGVPDRF TGSGYGTDFTFTITTVQSEDLAVYFCQQDHSSPFTFGSGTKLEIKRADAAPTVSIFPPSSEQ LTSGGASVVCFLNNFYPKDINVKWKIDGSERQNGVLNSWTDQDSKDSTYSMSSTLTLTKDEY ERHNSYTCEATHKTSTSPIVKSFNRNEC(SEQ ID NO: 38) muFR1-53LC DIQMTQTTSSLSASLGDRVTISCRASQDISNYLHWYQRKPDGTVKLLVYYTSRLQSGVPSRF SGSGSGTDYSLTISNLEQEDIATYFCQQGNSLPPTFGSGTKLEIKRADAAPTVSIFPPSSEQ LTSGGASVVCFLNNFYPKDINVKWKIDGSERQNGVLNSWTDQDSKDSTYSMSSTLTLTKDEY ERHNSYTCEATHKTSTSPIVKSFNRNEC(SEQ ID NO: 39) muFR1-62LC DIVMTQSQKFMSISVGDRVSVTCKASQNVGTNVAWYQQKPGQSPKTLIYSASSRYSGVPDRF TGSGSGTDFTLTISNVQSEDLADYFCHQYNSYPYTFGGGTKLEIKRADAAPTVSIFPPSSEQ LTSGGASVVCFLNNFYPKDINVKWKIDGSERQNGVLNSWTDQDSKDSTYSMSSTLTLTKDEY ERHNSYTCEATHKTSTSPIVKSFNRNEC(SEQ ID NO: 40)

Also provided are polypeptides that comprise: (a) a polypeptide havingat least about 90% sequence identity to SEQ ID NOs:33-36; and/or (b) apolypeptide having at least about 90% sequence identity to SEQ IDNOs:37-40. In certain embodiments, the polypeptide comprises apolypeptide having at least about 95%, at least about 96%, at leastabout 97%, at least about 98%, or at least about 99% sequence identityto SEQ ID NOs:33-40. Thus, in certain embodiments, the polypeptidecomprises (a) a polypeptide having at least about 95% sequence identityto SEQ ID NOs:33-36, and/or (b) a polypeptide having at least about 95%sequence identity to SEQ ID NOs:37-40. In certain embodiments, thepolypeptide comprises (a) a polypeptide having the amino acid sequenceof SEQ ID NOs:33-36; and/or (b) a polypeptide having the amino acidsequence of SEQ ID NOs:37-40. In certain embodiments, the polypeptide isan antibody and/or the polypeptide specifically binds FOLR1. In certainembodiments, the polypeptide is a murine, chimeric, or humanizedantibody that specifically binds FOLR1. In certain embodiments, thepolypeptide having a certain percentage of sequence identity to SEQ IDNOs:33-40 differs from SEQ ID NOs:33-40 by conservative amino acidsubstitutions only.

The affinity or avidity of an antibody for an antigen can be determinedexperimentally using any suitable method well known in the art, e.g.,cytometry (including flow cytometry), enzyme-linked immunoabsorbentassay (ELISA), or radioimmunoassay (RIA), or kinetics (e.g., surfaceplasmon resonance spectroscopy (BIACORE™) analysis). Direct bindingassays as well as competitive binding assay formats can be readilyemployed. (See, for example, Berzofsky, et al., “Antibody-AntigenInteractions,” In Fundamental Immunology, Paul, W. E., Ed., Raven Press:New York, N.Y. (1984); Kuby, Janis Immunology, W. H. Freeman andCompany: New York, N.Y. (1992); and methods described herein. Themeasured affinity of a particular antibody-antigen interaction can varyif measured under different conditions (e.g., salt concentration, pH,temperature). Thus, measurements of affinity and other antigen-bindingparameters (e.g., KD or Kd, K_(on), K_(off)) are made with standardizedsolutions of antibody and antigen, and a standardized buffer, as knownin the art and such as the buffer described herein.

In one aspect, binding assays can be performed using cytometry (e.g.,flow cytometry) on cells expressing the FOLR1 antigen on the surface.For example, FOLR1-positive cells such as SKOV3 were incubated withvarying concentrations of anti-FOLR1 antibodies using 1×10⁵ cells persample in 100 μL FACS buffer (RPMI-1640 medium supplemented with 2%normal goat serum). Then, the cells were pelleted, washed, and incubatedfor 1 h with 100 μL of FITC-conjugated goat-anti-mouse orgoat-anti-human IgG-antibody (such as is obtainable from, for exampleJackson Laboratory, 6 μg/mL in FACS buffer). The cells were pelletedagain, washed with FACS buffer and resuspended in 200 μL of PBScontaining 1% formaldehyde. Samples were acquired, for example, using aFACSCalibur flow cytometer with the HTS multiwell sampler and analyzedusing CellQuest Pro (all from BD Biosciences, San Diego, US). For eachsample the mean fluorescence intensity for FL1 (MFI) was exported andplotted against the antibody concentration in a semi-log plot togenerate a binding curve. A sigmoidal dose-response curve is fitted forbinding curves and EC50 values are calculated using programs such asGraphPad Prism v4 with default parameters (GraphPad software, San Diego,Calif.). EC50 values can be used as a measure for the apparentdissociation constant “Kd” or “KD” for each antibody.

Monoclonal antibodies can be prepared using hybridoma methods, such asthose described by Kohler and Milstein (1975) Nature 256:495. Using thehybridoma method, a mouse, hamster, or other appropriate host animal, isimmunized as described above to elicit the production by lymphocytes ofantibodies that will specifically bind to an immunizing antigen.Lymphocytes can also be immunized in vitro. Following immunization, thelymphocytes are isolated and fused with a suitable myeloma cell lineusing, for example, polyethylene glycol, to form hybridoma cells thatcan then be selected away from unfused lymphocytes and myeloma cells.Hybridomas that produce monoclonal antibodies directed specificallyagainst a chosen antigen as determined by immunoprecipitation,immunoblotting, or by an in vitro binding assay (e.g., radioimmunoassay(RIA); enzyme-linked immunosorbent assay (ELISA)) can then be propagatedeither in vitro culture using standard methods (Goding, MonoclonalAntibodies: Principles and Practice, Academic Press, 1986) or in vivo asascites tumors in an animal. The monoclonal antibodies can then bepurified from the culture medium or ascites fluid as described forpolyclonal antibodies.

Alternatively monoclonal antibodies can also be made using recombinantDNA methods as described in U.S. Pat. No. 4,816,567. The polynucleotidesencoding a monoclonal antibody are isolated from mature B-cells orhybridoma cells, such as by RT-PCR using oligonucleotide primers thatspecifically amplify the genes encoding the heavy and light chains ofthe antibody, and their sequence is determined using conventionalprocedures. The isolated polynucleotides encoding the heavy and lightchains are then cloned into suitable expression vectors, which whentransfected into host cells such as E. coli cells, simian COS cells,Chinese hamster ovary (CHO) cells, or myeloma cells that do nototherwise produce immunoglobulin protein, monoclonal antibodies aregenerated by the host cells. Also, recombinant monoclonal antibodies orfragments thereof of the desired species can be isolated from phagedisplay libraries expressing CDRs of the desired species as described(McCafferty et al., 1990, Nature, 348:552-554; Clackson et al., 1991,Nature, 352:624-628; and Marks et al., 1991, J. Mol. Biol.,222:581-597).

The polynucleotide(s) encoding a monoclonal antibody can further bemodified in a number of different manners using recombinant DNAtechnology to generate alternative antibodies. In some embodiments, theconstant domains of the light and heavy chains of, for example, a mousemonoclonal antibody can be substituted 1) for those regions of, forexample, a human antibody to generate a chimeric antibody or 2) for anon-immunoglobulin polypeptide to generate a fusion antibody. In someembodiments, the constant regions are truncated or removed to generatethe desired antibody fragment of a monoclonal antibody. Site-directed orhigh-density mutagenesis of the variable region can be used to optimizespecificity, affinity, etc. of a monoclonal antibody.

In some embodiments, the monoclonal antibody against the human FOLR1 isa humanized antibody. In certain embodiments, such antibodies are usedtherapeutically to reduce antigenicity and HAMA (human anti-mouseantibody) responses when administered to a human subject.

Methods for engineering, humanizing or resurfacing non-human or humanantibodies can also be used and are well known in the art. A humanized,resurfaced or similarly engineered antibody can have one or more aminoacid residues from a source that is non-human, e.g., but not limited to,mouse, rat, rabbit, non-human primate or other mammal. These non-humanamino acid residues are replaced by residues that are often referred toas “import” residues, which are typically taken from an “import”variable, constant or other domain of a known human sequence.

Such imported sequences can be used to reduce immunogenicity or reduce,enhance or modify binding, affinity, on-rate, off-rate, avidity,specificity, half-life, or any other suitable characteristic, as knownin the art. In general, the CDR residues are directly and mostsubstantially involved in influencing FOLR1 binding. Accordingly, partor all of the non-human or human CDR sequences are maintained while thenon-human sequences of the variable and constant regions can be replacedwith human or other amino acids.

Antibodies can also optionally be humanized, resurfaced, engineered orhuman antibodies engineered with retention of high affinity for theantigen FOLR1 and other favorable biological properties. To achieve thisgoal, humanized (or human) or engineered anti-FOLR1 antibodies andresurfaced antibodies can be optionally prepared by a process ofanalysis of the parental sequences and various conceptual humanized andengineered products using three-dimensional models of the parental,engineered, and humanized sequences. Three-dimensional immunoglobulinmodels are commonly available and are familiar to those skilled in theart. Computer programs are available which illustrate and displayprobable three-dimensional conformational structures of selectedcandidate immunoglobulin sequences. Inspection of these displays permitsanalysis of the likely role of the residues in the functioning of thecandidate immunoglobulin sequence, i.e., the analysis of residues thatinfluence the ability of the candidate immunoglobulin to bind itsantigen, such as FOLR1. In this way, framework (FR) residues can beselected and combined from the consensus and import sequences so thatthe desired antibody characteristic, such as increased affinity for thetarget antigen(s), is achieved.

Humanization, resurfacing or engineering of antibodies of the presentinvention can be performed using any known method, such as but notlimited to those described in, Winter (Jones et al., Nature 321:522(1986); Riechmann et al., Nature 332:323 (1988); Verhoeyen et al.,Science 239:1534 (1988)), Sims et al., J. Immunol. 151: 2296 (1993);Chothia and Lesk, J. Mol. Biol. 196:901 (1987), Carter et al., Proc.Natl. Acad. Sci. U.S.A. 89:4285 (1992); Presta et al., J. Immunol.151:2623 (1993), Roguska et al., Proc. Natl. Acad. Sci., USA,91(3):969-973 (1994), Roguska et al., Protein Eng. 9(10):895-904 (1996),U.S. Pat. Nos. 5,639,641, 5,723,323; 5,976,862; 5,824,514; 5,817,483;5,814,476; 5,763,192; 5,723,323; 5,766,886; 5,714,352; 6,204,023;6,180,370; 5,693,762; 5,530,101; 5,585,089; 5,225,539; 4,816,567; PCT/:US98/16280; US96/18978; US91/09630; US91/05939; US94/01234; GB89/01334;GB91/01134; GB92/01755; WO90/14443; WO90/14424; WO90/14430; EP 229246;U.S. Pat. Nos. 7,557,189; 7,538,195; and 7,342,110, each of which isentirely incorporated herein by reference, including the referencescited therein.

In certain alternative embodiments, the antibody to FOLR1 is a humanantibody. Human antibodies can be directly prepared using varioustechniques known in the art. Immortalized human B lymphocytes immunizedin vitro or isolated from an immunized individual that produce anantibody directed against a target antigen can be generated (See, e.g.,Cole et al., Monoclonal Antibodies and Cancer Therapy, Alan R. Liss, p.77 (1985); Boemer et al., 1991, J. Immunol., 147 (1):86-95; and U.S.Pat. No. 5,750,373). Also, the human antibody can be selected from aphage library, where that phage library expresses human antibodies, asdescribed, for example, in Vaughan et al., 1996, Nat. Biotech.,14:309-314, Sheets et al., 1998, Proc. Nat'l. Acad. Sci., 95:6157-6162,Hoogenboom and Winter, 1991, J. Mol. Biol., 227:381, and Marks et al.,1991, J. Mol. Biol., 222:581). Techniques for the generation and use ofantibody phage libraries are also described in U.S. Pat. Nos. 5,969,108,6,172,197, 5,885,793, 6,521,404; 6,544,731; 6,555,313; 6,582,915;6,593,081; 6,300,064; 6,653,068; 6,706,484; and 7,264,963; and Rothe etal., 2007, J. Mol. Bio., doi:10.1016/j.jmb.2007.12.018 (each of which isincorporated by reference in its entirety). Affinity maturationstrategies and chain shuffling strategies (Marks et al., 1992,Bio/Technology 10:779-783, incorporated by reference in its entirety)are known in the art and can be employed to generate high affinity humanantibodies.

Humanized antibodies can also be made in transgenic mice containinghuman immunoglobulin loci that are capable upon immunization ofproducing the full repertoire of human antibodies in the absence ofendogenous immunoglobulin production. This approach is described in U.S.Pat. Nos. 5,545,807; 5,545,806; 5,569,825; 5,625,126; 5,633,425; and5,661,016.

This invention also encompasses bispecific antibodies that specificallyrecognize a human folate receptor 1. Bispecific antibodies areantibodies that are capable of specifically recognizing and binding atleast two different epitopes. The different epitopes can either bewithin the same molecule (e.g., the same human folate receptor 1) or ondifferent molecules, for example, the antibodies can specificallyrecognize and bind a human folate receptor 1 as well as, for example, 1)an effector molecule on a leukocyte such as a T-cell receptor (e.g.,CD3) or Fc receptor (e.g., CD64, CD32, or CD16) or 2) a cytotoxic agentas described in detail below.

Exemplary bispecific antibodies can bind to two different epitopes, atleast one of which originates in a polypeptide of the invention.Alternatively, an anti-antigenic arm of an immunoglobulin molecule canbe combined with an arm which binds to a triggering molecule on aleukocyte such as a T cell receptor molecule (e.g., CD2, CD3, CD28, orB7), or Fc receptors for IgG so as to focus cellular defense mechanismsto the cell expressing the particular antigen. Bispecific antibodies canalso be used to direct cytotoxic agents to cells which express aparticular antigen. These antibodies possess an antigen-binding arm andan arm which binds a cytotoxic agent or a radionuclide chelator, such asEOTUBE, DPTA, DOTA, or TETA. Techniques for making bispecific antibodiesare common in the art (Millstein et al., 1983, Nature 305:537-539;Brennan et al., 1985, Science 229:81; Suresh et al, 1986, Methods inEnzymol. 121:120; Traunecker et al., 1991, EMBO J. 10:3655-3659; Shalabyet al., 1992, J. Exp. Med. 175:217-225; Kostelny et al., 1992, J.Immunol. 148:1547-1553; Gruber et al., 1994, J. Immunol. 152:5368; andU.S. Pat. No. 5,731,168). Antibodies with more than two valencies arealso contemplated. For example, trispecific antibodies can be prepared(Tutt et al., J. Immunol. 147:60 (1991)). Thus, in certain embodimentsthe antibodies to FOLR1 are multispecific.

In certain embodiments are provided an antibody fragment to, forexample, increase tumor penetration. Various techniques are known forthe production of antibody fragments. Traditionally, these fragments arederived via proteolytic digestion of intact antibodies (for exampleMorimoto et al., 1993, Journal of Biochemical and Biophysical Methods24:107-117; Brennan et al., 1985, Science, 229:81). In certainembodiments, antibody fragments are produced recombinantly. Fab, Fv, andscFv antibody fragments can all be expressed in and secreted from E.coli or other host cells, thus allowing the production of large amountsof these fragments. Such antibody fragments can also be isolated fromthe antibody phage libraries discussed above. The antibody fragment canalso be linear antibodies as described in U.S. Pat. No. 5,641,870, forexample, and can be monospecific or bispecific. Other techniques for theproduction of antibody fragments will be apparent to the skilledpractitioner.

According to the present invention, techniques can be adapted for theproduction of single-chain antibodies specific to human folate receptor1 (see U.S. Pat. No. 4,946,778). In addition, methods can be adapted forthe construction of Fab expression libraries (Huse, et al., Science246:1275-1281 (1989)) to allow rapid and effective identification ofmonoclonal Fab fragments with the desired specificity for a folate 1receptor, or derivatives, fragments, analogs or homologs thereof.Antibody fragments can be produced by techniques in the art including,but not limited to: (a) a F(ab′)2 fragment produced by pepsin digestionof an antibody molecule; (b) a Fab fragment generated by reducing thedisulfide bridges of an F(ab′)2 fragment, (c) a Fab fragment generatedby the treatment of the antibody molecule with papain and a reducingagent, and (d) Fv fragments.

It can further be desirable, especially in the case of antibodyfragments, to modify an antibody in order to increase its serumhalf-life. This can be achieved, for example, by incorporation of asalvage receptor binding epitope into the antibody fragment by mutationof the appropriate region in the antibody fragment or by incorporatingthe epitope into a peptide tag that is then fused to the antibodyfragment at either end or in the middle (e.g., by DNA or peptidesynthesis).

Heteroconjugate antibodies are also within the scope of the presentinvention. Heteroconjugate antibodies are composed of two covalentlyjoined antibodies. Such antibodies have, for example, been proposed totarget immune cells to unwanted cells (U.S. Pat. No. 4,676,980). It iscontemplated that the antibodies can be prepared in vitro using knownmethods in synthetic protein chemistry, including those involvingcrosslinking agents. For example, immunotoxins can be constructed usinga disulfide exchange reaction or by forming a thioether bond. Examplesof suitable reagents for this purpose include iminothiolate andmethyl-4-mercaptobutyrimidate.

For the purposes of the present invention, it should be appreciated thatmodified antibodies can comprise any type of variable region thatprovides for the association of the antibody with the polypeptides of ahuman FOLR1. In this regard, the variable region can comprise or bederived from any type of mammal that can be induced to mount a humoralresponse and generate immunoglobulins against the desired tumorassociated antigen. As such, the variable region of the modifiedantibodies can be, for example, of human, murine, non-human primate(e.g., cynomolgus monkeys, macaques, etc.) or lupine origin. In someembodiments both the variable and constant regions of the modifiedimmunoglobulins are human. In other embodiments the variable regions ofcompatible antibodies (usually derived from a non-human source) can beengineered or specifically tailored to improve the binding properties orreduce the immunogenicity of the molecule. In this respect, variableregions useful in the present invention can be humanized or otherwisealtered through the inclusion of imported amino acid sequences.

In certain embodiments, the variable domains in both the heavy and lightchains are altered by at least partial replacement of one or more CDRsand, if necessary, by partial framework region replacement and sequencechanging. Although the CDRs can be derived from an antibody of the sameclass or even subclass as the antibody from which the framework regionsare derived, it is envisaged that the CDRs will be derived from anantibody of different class and in certain embodiments from an antibodyfrom a different species. It may not be necessary to replace all of theCDRs with the complete CDRs from the donor variable region to transferthe antigen-binding capacity of one variable domain to another. Rather,it may only be necessary to transfer those residues that are necessaryto maintain the activity of the antigen-binding site. Given theexplanations set forth in U.S. Pat. Nos. 5,585,089, 5,693,761 and5,693,762, it will be well within the competence of those skilled in theart, either by carrying out routine experimentation or by trial anderror testing to obtain a functional antibody with reducedimmunogenicity.

Alterations to the variable region notwithstanding, those skilled in theart will appreciate that the modified antibodies of this invention willcomprise antibodies (e.g., full-length antibodies or immunoreactivefragments thereof) in which at least a fraction of one or more of theconstant region domains has been deleted or otherwise altered so as toprovide desired biochemical characteristics such as increased tumorlocalization or reduced serum half-life when compared with an antibodyof approximately the same immunogenicity comprising a native orunaltered constant region. In some embodiments, the constant region ofthe modified antibodies will comprise a human constant region.Modifications to the constant region compatible with this inventioncomprise additions, deletions or substitutions of one or more aminoacids in one or more domains. That is, the modified antibodies disclosedherein can comprise alterations or modifications to one or more of thethree heavy chain constant domains (CH1, CH2 or CH3) and/or to the lightchain constant domain (CL). In some embodiments, modified constantregions wherein one or more domains are partially or entirely deletedare contemplated. In some embodiments, the modified antibodies willcomprise domain deleted constructs or variants wherein the entire CH2domain has been removed (ΔCH2 constructs). In some embodiments, theomitted constant region domain will be replaced by a short amino acidspacer (e.g., 10 residues) that provides some of the molecularflexibility typically imparted by the absent constant region.

It will be noted that in certain embodiments, the modified antibodiescan be engineered to fuse the CH3 domain directly to the hinge region ofthe respective modified antibodies. In other constructs it may bedesirable to provide a peptide spacer between the hinge region and themodified CH2 and/or CH3 domains. For example, compatible constructscould be expressed wherein the CH2 domain has been deleted and theremaining CH3 domain (modified or unmodified) is joined to the hingeregion with a 5-20 amino acid spacer. Such a spacer can be added, forinstance, to ensure that the regulatory elements of the constant domainremain free and accessible or that the hinge region remains flexible.However, it should be noted that amino acid spacers can, in some cases,prove to be immunogenic and elicit an unwanted immune response againstthe construct. Accordingly, in certain embodiments, any spacer added tothe construct will be relatively non-immunogenic, or even omittedaltogether, so as to maintain the desired biochemical qualities of themodified antibodies.

Besides the deletion of whole constant region domains, it will beappreciated that the antibodies of the present invention can be providedby the partial deletion or substitution of a few or even a single aminoacid. For example, the mutation of a single amino acid in selected areasof the CH2 domain may be enough to substantially reduce Fc binding andthereby increase tumor localization. Similarly, it may be desirable tosimply delete that part of one or more constant region domains thatcontrol the effector function (e.g., complement C1Q binding) to bemodulated. Such partial deletions of the constant regions can improveselected characteristics of the antibody (serum half-life) while leavingother desirable functions associated with the subject constant regiondomain intact. Moreover, as alluded to above, the constant regions ofthe disclosed antibodies can be modified through the mutation orsubstitution of one or more amino acids that enhances the profile of theresulting construct. In this respect it may be possible to disrupt theactivity provided by a conserved binding site (e.g., Fc binding) whilesubstantially maintaining the configuration and immunogenic profile ofthe modified antibody. Certain embodiments can comprise the addition ofone or more amino acids to the constant region to enhance desirablecharacteristics such as decreasing or increasing effector function orprovide for more cytotoxin or carbohydrate attachment. In suchembodiments it can be desirable to insert or replicate specificsequences derived from selected constant region domains.

The present invention further embraces variants and equivalents whichare substantially homologous to the chimeric, humanized and humanantibodies, or antibody fragments thereof, set forth herein. These cancontain, for example, conservative substitution mutations, i.e., thesubstitution of one or more amino acids by similar amino acids. Forexample, conservative substitution refers to the substitution of anamino acid with another within the same general class such as, forexample, one acidic amino acid with another acidic amino acid, one basicamino acid with another basic amino acid or one neutral amino acid byanother neutral amino acid. What is intended by a conservative aminoacid substitution is well known in the art.

The polypeptides of the present invention can be recombinantpolypeptides, natural polypeptides, or synthetic polypeptides comprisingan antibody, or fragment thereof, against a human FOLR1. It will berecognized in the art that some amino acid sequences of the inventioncan be varied without significant effect of the structure or function ofthe protein. Thus, the invention further includes variations of thepolypeptides which show substantial activity or which include regions ofan antibody, or fragment thereof, against a human folate receptorprotein. Such mutants include deletions, insertions, inversions,repeats, and type substitutions.

The polypeptides and analogs can be further modified to containadditional chemical moieties not normally part of the protein. Thosederivatized moieties can improve the solubility, the biological halflife or absorption of the protein. The moieties can also reduce oreliminate any desirable side effects of the proteins and the like. Anoverview for those moieties can be found in REMINGTON'S PHARMACEUTICALSCIENCES, 20th ed., Mack Publishing Co., Easton, Pa. (2000).

The isolated polypeptides described herein can be produced by anysuitable method known in the art. Such methods range from direct proteinsynthetic methods to constructing a DNA sequence encoding isolatedpolypeptide sequences and expressing those sequences in a suitabletransformed host. In some embodiments, a DNA sequence is constructedusing recombinant technology by isolating or synthesizing a DNA sequenceencoding a wild-type protein of interest. Optionally, the sequence canbe mutagenized by site-specific mutagenesis to provide functionalanalogs thereof. See, e.g., Zoeller et al., Proc. Nat'l. Acad. Sci. USA81:5662-5066 (1984) and U.S. Pat. No. 4,588,585.

In some embodiments a DNA sequence encoding a polypeptide of interestwould be constructed by chemical synthesis using an oligonucleotidesynthesizer. Such oligonucleotides can be designed based on the aminoacid sequence of the desired polypeptide and selecting those codons thatare favored in the host cell in which the recombinant polypeptide ofinterest will be produced. Standard methods can be applied to synthesizean isolated polynucleotide sequence encoding an isolated polypeptide ofinterest. For example, a complete amino acid sequence can be used toconstruct a back-translated gene. Further, a DNA oligomer containing anucleotide sequence coding for the particular isolated polypeptide canbe synthesized. For example, several small oligonucleotides coding forportions of the desired polypeptide can be synthesized and then ligated.The individual oligonucleotides typically contain 5′ or 3′ overhangs forcomplementary assembly.

Once assembled (by synthesis, site-directed mutagenesis or anothermethod), the polynucleotide sequences encoding a particular isolatedpolypeptide of interest will be inserted into an expression vector andoperatively linked to an expression control sequence appropriate forexpression of the protein in a desired host. Proper assembly can beconfirmed by nucleotide sequencing, restriction mapping, and expressionof a biologically active polypeptide in a suitable host. As is wellknown in the art, in order to obtain high expression levels of atransfected gene in a host, the gene must be operatively linked totranscriptional and translational expression control sequences that arefunctional in the chosen expression host.

In certain embodiments, recombinant expression vectors are used toamplify and express DNA encoding antibodies, or fragments thereof,against human FOLR1. Recombinant expression vectors are replicable DNAconstructs which have synthetic or cDNA-derived DNA fragments encoding apolypeptide chain of an anti-FOLR1 antibody, or fragment thereof,operatively linked to suitable transcriptional or translationalregulatory elements derived from mammalian, microbial, viral or insectgenes. A transcriptional unit generally comprises an assembly of (1) agenetic element or elements having a regulatory role in gene expression,for example, transcriptional promoters or enhancers, (2) a structural orcoding sequence which is transcribed into mRNA and translated intoprotein, and (3) appropriate transcription and translation initiationand termination sequences, as described in detail below. Such regulatoryelements can include an operator sequence to control transcription. Theability to replicate in a host, usually conferred by an origin ofreplication, and a selection gene to facilitate recognition oftransformants can additionally be incorporated. DNA regions areoperatively linked when they are functionally related to each other. Forexample, DNA for a signal peptide (secretory leader) is operativelylinked to DNA for a polypeptide if it is expressed as a precursor whichparticipates in the secretion of the polypeptide; a promoter isoperatively linked to a coding sequence if it controls the transcriptionof the sequence; or a ribosome binding site is operatively linked to acoding sequence if it is positioned so as to permit translation.Structural elements intended for use in yeast expression systems includea leader sequence enabling extracellular secretion of translated proteinby a host cell. Alternatively, where recombinant protein is expressedwithout a leader or transport sequence, it can include an N-terminalmethionine residue. This residue can optionally be subsequently cleavedfrom the expressed recombinant protein to provide a final product.

The choice of expression control sequence and expression vector willdepend upon the choice of host. A wide variety of expression host/vectorcombinations can be employed. Useful expression vectors for eukaryotichosts, include, for example, vectors comprising expression controlsequences from SV40, bovine papilloma virus, adenovirus andcytomegalovirus. Useful expression vectors for bacterial hosts includeknown bacterial plasmids, such as plasmids from Escherichia coli,including pCR 1, pBR322, pMB9 and their derivatives, wider host rangeplasmids, such as M13 and filamentous single-stranded DNA phages.

Suitable host cells for expression of a FOLR1-binding polypeptide orantibody (or a FOLR1 protein to use as an antigen) include prokaryotes,yeast, insect or higher eukaryotic cells under the control ofappropriate promoters. Prokaryotes include gram negative or grampositive organisms, for example E. coli or bacilli. Higher eukaryoticcells include established cell lines of mammalian origin as describedbelow. Cell-free translation systems could also be employed. Appropriatecloning and expression vectors for use with bacterial, fungal, yeast,and mammalian cellular hosts are described by Pouwels et al. (CloningVectors: A Laboratory Manual, Elsevier, N. Y., 1985), the relevantdisclosure of which is hereby incorporated by reference. Additionalinformation regarding methods of protein production, including antibodyproduction, can be found, e.g., in U.S. Patent Publication No.2008/0187954, U.S. Pat. Nos. 6,413,746 and 6,660,501, and InternationalPatent Publication No. WO 04009823, each of which is hereby incorporatedby reference herein in its entirety.

Various mammalian or insect cell culture systems are also advantageouslyemployed to express recombinant protein. Expression of recombinantproteins in mammalian cells can be performed because such proteins aregenerally correctly folded, appropriately modified and completelyfunctional. Examples of suitable mammalian host cell lines includeHEK-293 and HEK-293T, the COS-7 lines of monkey kidney cells, describedby Gluzman (Cell 23:175, 1981), and other cell lines including, forexample, L cells, C127, 3T3, Chinese hamster ovary (CHO), HeLa and BHKcell lines. Mammalian expression vectors can comprise nontranscribedelements such as an origin of replication, a suitable promoter andenhancer linked to the gene to be expressed, and other 5′ or 3′ flankingnontranscribed sequences, and 5′ or 3′ nontranslated sequences, such asnecessary ribosome binding sites, a polyadenylation site, splice donorand acceptor sites, and transcriptional termination sequences.Baculovirus systems for production of heterologous proteins in insectcells are reviewed by Luckow and Summers, Bio/Technology 6:47 (1988).

The proteins produced by a transformed host can be purified according toany suitable method. Such standard methods include chromatography (e.g.,ion exchange, affinity and sizing column chromatography),centrifugation, differential solubility, or by any other standardtechnique for protein purification. Affinity tags such as hexahistidine,maltose binding domain, influenza coat sequence andglutathione-S-transferase can be attached to the protein to allow easypurification by passage over an appropriate affinity column. Isolatedproteins can also be physically characterized using such techniques asproteolysis, nuclear magnetic resonance and x-ray crystallography.

For example, supernatants from systems which secrete recombinant proteininto culture media can be first concentrated using a commerciallyavailable protein concentration filter, for example, an Amicon orMillipore Pellicon ultrafiltration unit. Following the concentrationstep, the concentrate can be applied to a suitable purification matrix.Alternatively, an anion exchange resin can be employed, for example, amatrix or substrate having pendant diethylaminoethyl (DEAE) groups. Thematrices can be acrylamide, agarose, dextran, cellulose or other typescommonly employed in protein purification. Alternatively, a cationexchange step can be employed. Suitable cation exchangers includevarious insoluble matrices comprising sulfopropyl or carboxymethylgroups. Finally, one or more reversed-phase high performance liquidchromatography (RP-HPLC) steps employing hydrophobic RP-HPLC media,e.g., silica gel having pendant methyl or other aliphatic groups, can beemployed to further purify a FOLR1-binding agent. Some or all of theforegoing purification steps, in various combinations, can also beemployed to provide a homogeneous recombinant protein.

Recombinant protein produced in bacterial culture can be isolated, forexample, by initial extraction from cell pellets, followed by one ormore concentration, salting-out, aqueous ion exchange or size exclusionchromatography steps. High performance liquid chromatography (HPLC) canbe employed for final purification steps. Microbial cells employed inexpression of a recombinant protein can be disrupted by any convenientmethod, including freeze-thaw cycling, sonication, mechanicaldisruption, or use of cell lysing agents.

Methods known in the art for purifying antibodies and other proteinsalso include, for example, those described in U.S. Patent PublicationNos. 2008/0312425, 2008/0177048, and 2009/0187005, each of which ishereby incorporated by reference herein in its entirety.

IV. Polynucleotides

In certain embodiments, the invention encompasses polynucleotidescomprising polynucleotides that encode a polypeptide that specificallybinds a human FOLR1 receptor or a fragment of such a polypeptide. Forexample, the invention provides a polynucleotide comprising a nucleicacid sequence that encodes an antibody to a human FOLR1 or encodes afragment of such an antibody. The polynucleotides of the invention canbe in the form of RNA or in the form of DNA. DNA includes cDNA, genomicDNA, and synthetic DNA; and can be double-stranded or single-stranded,and if single stranded can be the coding strand or non-coding(anti-sense) strand. In some embodiments, the polynucleotide is a cDNAor a DNA lacking one more endogenous introns.

In some embodiments, a polynucleotide is a non-naturally occurringpolynucleotide. In some embodiments, a polynucleotide is recombinantlyproduced.

In certain embodiments, the polynucleotides are isolated. In certainembodiments, the polynucleotides are substantially pure. In someembodiments, a polynucleotide is purified from natural components.

The invention provides a polynucleotide comprising a polynucleotideencoding a polypeptide comprising a sequence selected from the groupconsisting of SEQ ID NOs:1-40. Also provided is a polynucleotideencoding a polypeptide having at least about 95%, at least about 96%, atleast about 97%, at least about 98%, or at least about 99% sequenceidentity to SEQ ID NOs: 1-40.

In certain embodiments the polynucleotides comprise the coding sequencefor the mature polypeptide fused in the same reading frame to apolynucleotide which aids, for example, in expression and secretion of apolypeptide from a host cell (e.g., a leader sequence which functions asa secretory sequence for controlling transport of a polypeptide from thecell). The polypeptide having a leader sequence is a preprotein and canhave the leader sequence cleaved by the host cell to form the matureform of the polypeptide. The polynucleotides can also encode for aproprotein which is the mature protein plus additional 5′ amino acidresidues. A mature protein having a prosequence is a proprotein and isan inactive form of the protein. Once the prosequence is cleaved anactive mature protein remains.

In certain embodiments the polynucleotides comprise the coding sequencefor the mature polypeptide fused in the same reading frame to a markersequence that allows, for example, for purification of the encodedpolypeptide. For example, the marker sequence can be a hexahistidine tagsupplied by a pQE-9 vector to provide for purification of the maturepolypeptide fused to the marker in the case of a bacterial host, or themarker sequence can be a hemagglutinin (HA) tag derived from theinfluenza hemagglutinin protein when a mammalian host (e.g., COS-7cells) is used.

The present invention further relates to variants of the hereinabovedescribed polynucleotides encoding, for example, fragments, analogs, andderivatives.

The polynucleotide variants can contain alterations in the codingregions, non-coding regions, or both. In some embodiments thepolynucleotide variants contain alterations which produce silentsubstitutions, additions, or deletions, but do not alter the propertiesor activities of the encoded polypeptide. In some embodiments,nucleotide variants are produced by silent substitutions due to thedegeneracy of the genetic code. Polynucleotide variants can be producedfor a variety of reasons, e.g., to optimize codon expression for aparticular host (change codons in the human mRNA to those preferred by abacterial host such as E. coli).

Vectors and cells comprising the polynucleotides described herein arealso provided.

V. Detection

When a sandwich ELISA format is used, the capture antibody will beunlabeled. The detection antibody will be either directly labeled, ordetected indirectly by addition (after washing off excess detectionantibody) of a molar excess of a second, labeled antibody directedagainst the first antibody.

The label used for the detection antibody is any detectablefunctionality that does not interfere with the binding of the FOLR1antibodies. Examples of suitable labels are those numerous labels knownfor use in immunoassay, including moieties that may be detecteddirectly, such as fluorochrome, chemiluminescent, and radioactivelabels, as well as moieties, such as enzymes, that must be reacted orderivatized to be detected. Examples of such labels include theradioisotopes ³²P, ¹⁴C, ¹²⁵I, ³H, and ¹³¹I, fluorophores such as rareearth chelates or fluorescein and its derivatives, rhodamine and itsderivatives, dansyl, umbelliferone, luciferases, e.g., fireflyluciferase and bacterial luciferase (U.S. Pat. No. 4,737,456),luciferin, 2,3-dihydrophthalazinediones, horseradish peroxidase (HRP),alkaline phosphatase, β-galactosidase, glucoamylase, lysozyme,saccharide oxidases, e.g., glucose oxidase, galactose oxidase, andglucose-6-phosphate dehydrogenase, heterocyclic oxidases such as uricaseand xanthine oxidase, coupled with an enzyme that employs hydrogenperoxide to oxidize a dye precursor such as HRP, lactoperoxidase, ormicroperoxidase, biotin/avidin, biotin/streptavidin,biotin/Streptavidin-β-galactosidase with MUG, spin labels, bacteriophagelabels, stable free radicals, and the like. As noted above, thefluorimetric detection is one example.

Conventional methods are available to bind these labels covalently toproteins or polypeptides. For instance, coupling agents such asdialdehydes, carbodiimides, dimaleimides, bis-imidates, bis-diazotizedbenzidine, and the like may be used to tag the antibodies with theabove-described fluorescent, chemiluminescent, and enzyme labels. See,for example, U.S. Pat. No. 3,940,475 (fluorimetry) and U.S. Pat. No.3,645,090 (enzymes); Hunter et al. Nature 144:945 (1962); David et al.Biochemistry 13:1014-1021 (1974); Pain et al. J. Immunol. Methods40:219-230 (1981); and Nygren J. Histochem. and Cytochem. 30:407-412(1982). In certain embodiments, labels herein are fluorescent toincrease amplification and sensitivity to 8 pg/ml, more preferablybiotin with streptavidin-β-galactosidase and MUG for amplifying thesignal. In certain embodiments, a colorimetric label is used, e.g.,where the detectable antibody is biotinylated and the detection means isavidin or streptavidin-peroxidase and 3,3′,5,5′-tetramethyl benzidine.

The conjugation of such label, including the enzymes, to the antibody isa standard manipulative procedure for one of ordinary skill inimmunoassay techniques. See, for example, O'Sullivan et al. “Methods forthe Preparation of Enzyme-antibody Conjugates for Use in EnzymeImmunoassay,” in Methods in Enzymology, ed. J. J. Langone and H. VanVunakis, Vol. 73 (Academic Press, New York, N.Y., 1981), pp. 147-166.

Following the addition of last labeled antibody, the amount of boundantibody is determined by removing excess unbound labeled antibodythrough washing and then measuring the amount of the attached labelusing a detection method appropriate to the label, and correlating themeasured amount with the amount of shed FOLR1 or FOLR1 on circulatingtumor cells in the biological sample. For example, in the case ofenzymes, the amount of color developed and measured will be a directmeasurement of the amount of shed FOLR1 present or FOLR1 present oncirculating tumor cells. Specifically, if HRP is the label, the colorcan be detected using the substrate 3,3′,5,5′-tetramethyl benzidine at450 nm absorbance.

VI. Circulating Tumor Cell Assays

The anti-FOLR1 antibodies described herein may also be used for thedetection of FOLR1 in a circulating tumor cell assay. Circulating tumorcells (CTCs) are cells that have shed into the vasculature from a tumorand circulate in the bloodstream. CTCs are present in circulation inextremely low concentrations. In general, CTC are enriched from patientblood or plasma by various techniques known in the art. CTCs may bestained for specific markers using methods known in the art including,but not limited to, cytometry (e.g., flow cytometry)-based methods andIHC-based methods. CTCs may be stained for protein markers unique to thetumor cells which allows for the identification and distinction of CTCsfrom normal blood cells. CTCs may also be stained for FOLR1 using theantibodies of the invention including, but not limited to, FR1-9 andFR1-13. CTC analysis may also include quantitative analysis of thenumber of CTCs and/or the number of FOLR1 positive CTCs. In the presentinvention, the FOLR1 antibodies described herein may be used to stainthe CTCs isolated from a subject having a cancer to measure the FOLR1present in the CTCs. An increase in FOLR1 expressing CTCs may helpidentify the subject as having a cancer that is likely to respond toFOLR1 based therapy or allow for optimization of a therapeutic regimenwith a FOLR1 antibody or Immunoconjugate. CTC FOLR1 quantitation canprovide information on the stage of tumor, response to therapy and/ordisease progression. It can be used as prognostic, predictive orpharmacodimamic biomarker. In addition, staining of CTCs for particularmarkers including, but not limited to FOLR1, may be used as a liquidbiopsy either alone or in combination with additional tumor markeranalysis of solid biopsy samples.

VII. Kits

As a matter of convenience, the assay method of this invention can beprovided in the form of a kit. Such a kit is a packaged combinationincluding the basic elements of: (a) a first reagent, which can be acapture reagent, comprised of the monoclonal antibodies against humanFOLR1; and/or (b) a second reagent which is a detection reagent. Thedetection reagent can also comprise FOLR1 monoclonal antibodies, but canalso comprise detectable (labeled or unlabeled) antibodies that bind toFOLR1. These basic elements are defined hereinabove and in the Examplesbelow.

In one embodiment wherein the first reagent and the second reagent areantibodies, antigen-binding fragments thereof, or polypeptides that bindto FOLR1, the first and second reagents are different antibodies,antigen-binding fragments thereof, or polypeptides. In one embodiment,the first reagent binds to a different FOLR1 epitope than the secondFOLR1 reagent. In one embodiment, neither the first reagent or thesecond reagent competitively inhibits the binding of an active agent(e.g., a an active agent comprising an huMOv19 antibody orantigen-binding fragment thereof) from binding to FOLR1.

In one embodiment, the kit further comprises a solid support for thecapture reagents, which can be provided as a separate element or onwhich the capture reagents are already immobilized. Hence, the captureantibodies in the kit can be immobilized on a solid support, or they canbe immobilized on such support that is included with the kit or providedseparately from the kit.

In one embodiment, the capture reagent is coated on a microtiter plate.The detection reagent can be labeled antibodies detected directly orunlabeled antibodies that are detected by labeled antibodies directedagainst the unlabeled antibodies raised in a different species. Wherethe label is an enzyme, the kit will ordinarily include substrates andcofactors required by the enzyme, and where the label is a fluorophore,a dye precursor that provides the detectable chromophore. Where thedetection reagent is unlabeled, the kit can further comprise a detectionmeans for the detectable antibodies, such as the labeled antibodiesdirected to the unlabeled antibodies, e.g., in a fluorimetric-detectedformat. Where the label is an enzyme, the kit will ordinarily includesubstrates and cofactors required by the enzyme, where the label is afluorophore, a dye precursor that provides the detectable chromophore,and where the label is biotin, an avidin such as avidin, streptavidin,or streptavidin conjugated to HRP or β-galactosidase with MUG.

In one embodiment, the capture reagent is the FOLR1 antibody FR1-9 andthe detection reagent is the FOLR1 antibody FR1-13. In anotherembodiment, the FR1-13 is biotinylated.

The kit also typically contains instructions for carrying out the assay,and/or FOLR1 protein, or fragments thereof (e.g., FOLR1 extracellulardomain or the FOLR1 extracellular domain and all or a part of the GPIlinkage domain) as an antigen standard, as well as other additives suchas stabilizers, washing and incubation buffers, and the like. In oneembodiment, the FOLR1 antigen standard is a FOLR1-Fc immunoadhesin. Thekit can also include instructions for detection and scoring of FOLR1expression.

The components of the kit will be provided in predetermined ratios, withthe relative amounts of the various reagents suitably varied to providefor concentrations in solution of the reagents that substantiallymaximize the sensitivity of the assay. Particularly, the reagents can beprovided as dry powders, usually lyophilized, including excipients,which on dissolution will provide for a reagent solution having theappropriate concentration for combining with the sample to be tested.

Embodiments of the present disclosure can be further defined byreference to the following non-limiting examples, which describe indetail preparation of certain antibodies of the present disclosure andmethods for using antibodies of the present disclosure. It will beapparent to those skilled in the art that many modifications, both tomaterials and methods, can be practiced without departing from the scopeof the present disclosure.

EXAMPLES

It is understood that the examples and embodiments described herein arefor illustrative purposes only and that various modifications or changesin light thereof will be suggested to persons skilled in the art and areto be included within the spirit and purview of this application.

Example 1 Development of Murine Anti-FOLR1 Antibodies

There were two different immunization/screening series. In the firstseries, mice were subcutaneously immunized with approximately 5×10⁶FOLR1-expressing KB cells (American Tissue Culture Collection, ATCCCCL-17). In the second series 300-19 cells expressing human FOLR1 ontheir surface were used to immunize mice. To make these cells, the humanFOLR1 amino acid sequence was obtained from the NCBI website (accessionNP_057937), then it was codon optimized and synthesized by Blue Heronbiotechnologies, flanked by EcoRI and Xba1 restriction sites tofacilitate cloning into the pSRa mammalian expression vector. 300-19cells, a pre-B cell line derived from a Balb/c mouse (Reth et al.,Nature, 317:353-355 (1985)), were transfected with the pSRa-FolR1expression plasmid to stably express high levels of human FOLR1 on thecell surface. Standard immunization protocols known to those of skill,for example, such as those used at ImmunoGen, Inc. were applied for bothseries. Immunized mice were boosted with antigen three days before beingsacrificed for hybridoma generation. Spleens from mice was collectedaccording to standard animal protocols, such as, for example grindingtissue between two sterile, frosted microscopic slides to obtain asingle cell suspension in RPMI-1640 medium. The spleen cells werecentrifuged, pelleted, washed, and fused with a murine myeloma, such as,for example P3X63Ag8.653 cells (Kearney et al., J. Immunol.,123:1548-1550 (1979)) using polyethylene glycol-1500 (Roche 783 641).The fused cells were resuspended in RPMI-1640 selection mediumcontaining hypoxanthine-aminopterin-thymidine (HAT) (Sigma H-0262) andselected for growth in 96-well flat-bottomed culture plates(Corning-Costar 3596, 0.2 ml of cell suspension per well) at 37° C. with5% CO₂. After 5 days of incubation, 0.1 ml of culture supernatant wereremoved from each well and replaced with 0.1 ml of RPMI-1640 mediumcontaining hypoxanthine-thymidine (HT) supplement (Sigma H-0137).Incubation at 37° C. with 5% CO₂ was continued until hybridoma cloneswere ready for antibody screening. Other techniques of immunization andhybridoma production can also be used, including those described inLangone et al. (Eds., “Immunochemical Techniques, Part I”, Methods inEnzymology, Academic Press, volume 121, Florida) and Harlow et al.(“Antibodies: A Laboratory Manual”; Cold Spring Harbor Laboratory Press,New York (1988)).

Example 2 Hybridoma Screening and Selection

FOLR1-300-19 cells transfected with human FOLR1 and KB cells were usedin the first and second series of screenings correspondingly. Culturesupernatants from the hybridoma were screened by flow cytometry forsecretion of mouse monoclonal antibodies that bind to FOLR1 positivecells, such as FOLR1-expressing 300-19 cells or KB cells, but not to theFOLR1 negative cells, such as non-transfected 300-19 cells. 0.1 ml ofhybridoma supernatants was incubated for 3 h with either FOLR1-positivecells or the non-transfected 300-19 cells (1×10⁵ cells per sample) in0.1 ml FACS buffer (RPMI-1640 medium supplemented with 2% normal goatserum). Then, the cells were centrifuged, pelleted, washed, andincubated for 1 hour with 0.1 ml of PE-conjugated goat anti mouseIgG-antibody (such as obtainable from, for example Jackson Laboratory, 6μg/mL in FACS buffer). The cells were centrifuged, pelleted again,washed with FACS buffer and resuspended in 0.2 ml of PBS containing 1%formaldehyde. Cell-associated fluorescence was measured using aFACSCalibur flow cytometer with the HTS multiwell sampler or a FACSarray flow cytometer and analyzed using CellQuest Pro (all from BDBiosciences, San Diego, US). Positive hybridoma clones were subcloned bylimiting dilution. One subclone from each hybridoma, which showed thesame reactivity against FOLR1 as the parental cells by flow cytometry,was chosen for subsequent analysis. Stable subclones were cultured andthe isotype of each secreted anti-FOLR1 antibody was identified usingcommercial isotyping reagents (Roche 1493027). Murine antibodies wereprotein A purified from cleared hybridoma media as described above.These antibodies were designated FR-1 antibodies.

One clone, muFR1-13, was identified as an anti-FOLR1 clone that (1) didnot compete or hinder the binding of Mov19 simultaneously to the sameantigen, and (2) had a high binding specificity to the target asdemonstrated by common flow cytometry techniques (FIGS. 2A and 2B).These two characteristics were necessary in the development of thisassay, and so clone muFR1-13 was chosen for use in the assay.

From the remaining 64 anti-FOLR1 clone panel, a second antibody wasrequired for the assay that held the same criteria as was necessary formuFR1-13. Additionally, the second antibody could not compete or hinderthe binding of muFR1-13 simultaneously to the same antigen (i.e., Mov19,muFR1-13 and the final clone must have all distinctly separateepitopes). To satisfy these conditions, a series of competition ELISAexperiments were conducted on the remaining panel of 65 anti-folateclones (FIG. 3A). If an antibody shares the same, or sterically similarepitope to the antibody being detected, a reduction in signal isobserved (FIG. 3B). Using this method, 5 antibodies of the 64 testedwere identified as having epitopes that compete with Mov19, and hencewere removed from further consideration.

The same method was repeated substituting Mov19 conjugated Biotin withmuFR1-13 conjugated Biotin (FIG. 4). Using this method, 6 additionalclones were identified as having epitopes that compete with muFR1-13,and hence were removed from further consideration. Of the remaining 53clones, 13 more clones were shown to have poor affinity and were removedfrom consideration.

The remaining 40 clones were screened using a similar ELISA format asshown in FIG. 1. The 40 clones were alternatively coated onto the assayplate in place of muFR1-9 in the diagram, and the resulting bindingcurves were analyzed shown in FIG. 5. Antibodies that contained thelowest half-maximal response (EC50) were considered to have the highestbinding specificity to FOLR1, and thus were chosen as the top candidatesfor the assay. The binding affinities of the top 4 clones assayed inthis method ranged from ˜1-5×10⁻⁹ M once new, higher quality materialswere available for testing.

Example 3 Murine Monoclonal Antibody Purification

Antibodies were purified from hybridoma subclone supernatants usingstandard methods, such as, for example Protein A or G chromatography(HiTrap Protein A or G HP, 1 mL, Amersham Biosciences). Briefly,supernatant was prepared for chromatography by the addition of 1/10volume of 1 M Tris/HCl buffer, pH 8.0. The pH-adjusted supernatant wasfiltered through a 0.22 μm filter membrane and loaded onto columnequilibrated with binding buffer (PBS, pH 7.3). The column was washedwith binding buffer until a stable baseline was obtained with noabsorbance at 280 nm. Antibody was eluted with 0.1 M acetic acid buffercontaining 0.15 M NaCl, pH 2.8, using a flow rate of 0.5 mL/min.Fractions of approximately 0.25 mL were collected and neutralized by theaddition of 1/10 volume of 1M Tris/HCl, pH 8.0. The peak fraction(s) wasdialyzed overnight twice against 1×PBS and sterilized by filteringthrough a 0.2 μm filter membrane. Purified antibody was quantified byabsorbance at A₂₈₀.

Example 4 Binding Characterization by Flow Cytometry

Binding specificity was tested by flow cytometry using purifiedantibodies. Each antibody was incubated for 3 hours with eitherFOLR1-expressing 300-19 cells or the non-transfected 300-19 cells (1×10⁵cells per sample) in 0.1 ml FACS buffer (RPMI-1640 medium supplementedwith 2% normal goat serum). Then, the cells were pelleted, washed, andincubated for 1 hour with 0.1 ml of FITC-conjugated goat anti-mouseIgG-antibody (such as is obtainable from, for example JacksonLaboratory, 6 μg/mL in FACS buffer). The cells were pelleted again,washed with FACS buffer and resuspended in 200 μL of PBS containing 1%formaldehyde. Samples were acquired using a FACSCalibur flow cytometerwith the HTS multiwell sampler or a FACS array flow cytometer andanalyzed using CellQuest Pro (all from BD Biosciences, San Diego, US).The FACS histograms of anti-FOLR1 antibodies showed a fluorescenceshift, while parental 300-19 cells did not. Also, no significantfluorescence shift was detected when either of the cell lines wasincubated only with FITC conjugated goat anti-human IgG-antibody alone.

Example 5 Cloning and Sequencing of the VL and VH Regions of muFR1-9 andFR1-53

Total cellular RNA was prepared from 5×10⁶ hybridoma cells using anRNeasy kit (QIAgen) according to the manufacturer's protocol. cDNA wassubsequently synthesized from total RNA using the SuperScript II cDNAsynthesis kit (Invitrogen). The procedure for the first round degeneratePCR reaction on the cDNA derived from hybridoma cells was based onmethods described in Wang et al. (2000) J Immunol Methods. January 13;233(1-2):167-77) and Co et al. (1992) J Immunol. February 15;148(4):1149-54)). VH sequences were amplified by PCR using the followingdegenerate primers: EcoMH1 CTTCCGGAATTCSARGTNMAGCTGSAGSAGTC (SEQ IDNO:45), EcoMH2 CTTCCGGAATTCSARGTNMAGCTGSAGSAGTCWGG (SEQ ID NO:41), andBamIgG1 GGAGGATCCATAGACAGATGGGGGTGTCGTTTTGGC (SEQ ID NO:42). VLsequences were amplified by PCR using the following degenerate primers:SacIMK GGAGCTCGAYATTGTGMTSACMCARWCTMCA (SEQ ID NO:43) and HindKLTATAGAGCTCAAGCTTGGATGGTGGGAAGATGGATACAGTTGGTGC (SEQ ID NO:44). (Mixedbases are defined as follows: N=G+A+T+C, S=G+C, Y=C+T, M=A+C, R=A+G,W=A+T).

The PCR reaction mixtures were then run on a 1% low melt agarose gel,the 300 to 400 by bands were excised, purified using Zymo DNA minicolumns, and sent to Agencourt Biosciences for sequencing. Therespective 5′ and 3′ PCR primers were used as sequencing primers tosequence the variable region cDNAs from both directions. The amino acidsequences of VH and VL regions were obtained by translating the DNAsequencing results with VectorNTI software.

The preliminary variable region cDNA sequences included 5′ end sequencesderived from the degenerate PCR primers rather than the murine antibodymRNA so sequence comparisons with mouse antibody germline sequencesfacilitated the identification and removal of these sequencingartifacts. The NCBI IgBlast site (www.ncbi.nlm.nih.gov/igblast/) wasutilized to search for the murine germline sequences from which thepreliminary antibody cDNA sequences were derived and the primer derived5′ end sequences were replaced with the corresponding germlinesequences. The cleaned up variable region sequences were then combinedwith the NCBI reference sequences for the murine kappa and IgG1 constantregions (accessions AJ294736.1 and D78344.1 respectively) to assembleexpected full length murine antibody sequences. The molecular weight ofthe expected murine FR1-9 and FR1-53 light and heavy chains were thencalculated and compared with the mass measured by liquidchromatography/mass spectrophotometric analysis (LC/MS).

The initial efforts to sequence the murine FR1-9 light chain, followingthe methods described above, proved unsuccessful so alternative methodswere employed. The light chain sequences of hybridomas related to FR1-9were used to design the KS77LClead PCR primer(ttttgagctctggattccagcctccagaggt) to anneal to the presumed leadersequence of the FR1-9 light chain framework. This leader primer PCRreaction and sequencing was performed as described above and yielded acomplete cDNA sequence encoding a light chain that matches the FR1-9light chain mass measured by LC/MS.

Example 6 FOLR1 Fc Fusion Control Sample

A human folate receptor 1 Fc fusion molecule was constructed as analternative soluble antigen source to the human folate binding proteintypically derived from human milk. The amino-terminus of the human FolR1cDNA, described in the immunization example above, was excised from thefull length sequence with an EcoRI and Pst1 restriction digest. Thisfragment contained the cDNA encoding the 233 amino acids from the Nterminal signal peptide to the residues just up stream of the GPIlinkage site of huFolR1 (NCBI accession NM_016731.2). A Pst1 to BamHIoligonucleotide linker facilitated the cloning of the FolR1 fragmentin-frame with the murine IgG2A hinge, CH2, and CH3 antibody constantregion sequences (NCBI accession P01863) in the pmuFc2ANL-EK mammalianexpression plasmid. The human FolR1-Fc fusion protein was then expressedby transient or stable transfections in mammalian host cell lines suchas HEK-293T or CHO cells. Since the 475 amino acid fusion proteincontains the murine IgG2A constant region, the molecule was purifiedfollowing the standard murine antibody purification procedures describedabove.

Example 7 Shed Antigen ELISA Assay

To assure that materials were continuously performing as expected, allantibodies were screened for binding by both ELISA and flow cytometrymethods known in the art. Flow cytometry was performed using FOLR1expressing human T47D cells cultured using in-vitro cell culturetechniques known in the art. The antibodies were bound to these cellsand detected indirectly using a goat anti-murine Alexa-fluor 488detection antibody on a FACScalibur machine (FIG. 6A-B). The samemethods were applied to the other antibodies, and it was determined thatthe final selected antibodies FR1-13 and FR1-9 showed an approximately1-3×10⁻⁹ M, and 2-4×10⁻⁹ binding affinity respectively by both methods.

It is important that the assay detect only FOLR1, and not FOLR2 orespecially FOLR3 (commonly found as a shed protein in human plasma),since Mov19 is specific for only FOLR1. To determine this, the top fourclones were screened by commercially available ELISA kits (FIGS. 7A-B).The positive control detection antibody shows a positive signal abovebackground indicating detection of FOLR2 or FOLR3. The remainingantibodies (FR1-9, FR1-53, FR1-62, FR1-64, & Mov19) do not produce asignal in the assay, and therefore do not bind to FOLR2 or FOLR3.

Additionally, the presence of folic acid bound to FOLR1 couldpotentially obscure the epitope of the chosen antibodies. To assure thatthe assay would detect FOLR1 in physiological amounts of folic acid inhuman blood, folic acid was pre-incubated with the FOLR1 standardpurified protein and added to the assay plate. As shown in FIG. 8, thepresence of folic acid had negligible impact on the detection affinityof the assay compared to positive controls containing no folic acid.Therefore, it was concluded that the assay could detect FOLR1 even inthe presence of bound folic acid.

Since none of the top four antibody clones (FR1-9, 53, 62, or 64) showedinterference with the binding of Mov19 or FR1-13, and because no adversebinding properties were observed in the presence of FOLR2, FOLR3, orfolic acid, these four candidates of the original 64 clones were viablefor use in the assay. Of these four clones, it was determined that cloneFR1-9 and FR1-53 had higher binding affinities compared to FR1-62 andFR1-64. Production of the FR1-53 antibody from its parent hybridomaproduced consistently poorer yield, and hence clone FR1-9 was chosen forits ease of antibody production, higher antibody purity, and percentmonomer.

In efforts to optimize the assay, a systematic approach was used inwhich concentrations of FR1-9, Biotinylated FR1-13, Strp-HRP, andrespective incubation times were optimized using FOLR1-Fc fusion proteinas the antigen standard. The FOLR1-Fc fusion is a fusion peptide ofhuFOLR1 and murine IgG2A hinge, CH2, CH3. Criteria for establishingoptimized conditions were reproducible signals with a high signal tonoise ratio, minimal matrix effects in human plasma samples, highrepeatability and precision and lowest limit of detection.

More specifically, the assay was performed by coating an assay platewith muFR1-9 at 2 μg/mL and incubated. After blocking with anon-specific protein, samples (including antigen standards and humanplasma samples) were added to the assay plates to incubate. Plates werethen washed and muFR1-13b detection antibody (2 μg/mL) was added to eachwell. Plates were washed again before adding a molar excess ofstreptavidin conjugated Horse Radish Peroxidase (1:5,000). The plate waswashed again before 3,3′,5,5′-Tetramethylbenzidine (TMB), was added. TMBreacted with the peroxidase to form a blue color, with an intensitycommensurate with the amount of FOLR1 present in the sample. Thereaction was stopped with an acid containing solution, which turned thecolor yellow. The assay was then read on a spectramax plate reader todetermine the intensity of the color reaction in each sample(absorbance). When necessary, a sigmoidal dose-response (variable slope)curve was generated with Graphpad Prism v5.04 software using the 4PLequation: Y=Bottom+(Top−Bottom)/1+10^ ((Log EC50−X)*Hill Slope for alldilution series.

To determine the adequacy of the final ELISA format, human ovariancancer patient plasma and non-tumor sourced human ascites samples weretested. In non-tumor bearing patients with ascites fluid, 15 sampleswere analyzed for the presence of FOLR1. No FOLR1 was detected by theassay in all 15 samples, and no false positives were observed due tomatrix effects (FIG. 9). Alternatively, these ascites samples hadpurified human FOLR1 protein added into them, and the subsequentdetection was performed. Recovery of the FOLR1 protein as determined bythe assay was greater than 85% of the known added amount (not shown).Therefore, it was assumed there were no interfering proteins innon-tumor associated human ascites fluid even with no dilution of thesample.

The same analysis was performed in pooled normal human plasma (pooledwas n=10 patients per lot). No endogenous FOLR1 was detected by theassay, and no interfering proteins were discovered in non-dilutedsamples of human plasma with added purified huFOLR1-Fc protein (FIG.10). Samples of human ovarian cancer plasma were provided by the DanaFarber Cancer Institute or Mass General Hospital. Of the 72 samplesanalyzed to date, 7 samples were identified as having detectable levelsof FOLR1 with a range of 0.7 to 30.6 nM. A representative analysis ofthis data is shown in FIG. 11. Here, three of eight samples containeddetectable levels of FOLR1 showing 0.74, 0.91 and 30.6 nM for samplesPB105, PB106, and PB109 respectively. The method for interpolation ofthis data from a relevant standard curve generated using huFOLR1-Fc isshown in FIG. 12.

Example 8 Circulating Tumor Cell Assay

Three cell lines with varying levels of FOLR1 expression were selectedas representative of high expression (KB), low expression (OVCAR3), andno expression (A549). Unlabeled FR1-9 and FR1-13, as well as acommercial anti-FOLR1 antibody (“commercial FRA”), were titrated, andoptimal titrations were determined for each of the antibodies usinglaser scanning cytometry (LSC) detection on the selected cell lines.Fluorescence was measured as mean fluorescence intensity (MFI) and isshown in FIG. 13. All three antibodies showed expression of folatereceptor in KB cells. Optimal dilutions were identified for eachantibody as follows: 1:5 for commercial FRA, 1:100 for muFR1-9, and1:200 for muFR1-13. Of the antibodies tested, the commercial antibodygave the best signal to background ration (8.0 versus 4.07 (muFR1-9) and4.19 (muFR1-13)), but only muFR1-9 showed a signal in the OVCAR3 cells(approximately 30% more signal than A549 cells). See FIG. 14.

For applications that include monitoring the treatment or efficacy withIMGN853, the antibody selected for use in a CTC assay should not competewith the antibody component of IMGN853 (i.e., huMov19 (M9346A)) forbinding to FOLR1. Competition assays were conducted to determine if anyof the antibodies competed with IMGN853 antibody for binding to FOLR1.For these assays, A549 (negative) and KB (high expressors) cells weretreated with the M9346A antibody or vehicle alone. Cells were thenwashed and stained with each of the three antibodies, and expression wasanalyzed using LSC. The results are provided in FIG. 15. Light bars(left) represent vehicle alone, and dark bars (right) represent IMGN853treated cells. If competition with the therapeutic IMGN853 exists, thenthe dark bar (right) will be lower than the light bar (left) in the KBcells. The results in FIG. 15 show that the commercial FRA antibodycompetes for binding with IMGN853 (˜66% drop in FRA signal), while themuFR1-9 and muFR1-13 antibodies were not affected by IMGN853 treatment.

Taken together, these results demonstrate that muFR1-9 and muFR1-13 didnot compete with IMGN853, thereby making them the more desirablecandidates for use in an assay that monitors FOLR1 levels in a bodilyfluid (e.g., blood or plasma), circulating tumor cell, or tissue sample,after treatment with IMGN853. In addition, muFR1-9 was more sensitiveand demonstrated the unique ability to detect expression in OVCAR3 cellswhich had low levels of expression and is the preferred candidateantibody for these types of assays.

Example 9 Detection of FOLR1 in Circulating Tumor Cells (CTCs) Isolatedfrom NSCLC and Ovarian Cancer Patients

Blood samples are drawn from ovarian cancer or NSCLC cancer patients atthe following time points: Screening (up to 28 days prior to baseline);Baseline; Prior to Cycle 3; and End of Cycle 4. CTCs are enriched fromthe samples and stained for CK, CD45, nuclei, and FOLR1 using theantibodies and dilutions described in Example 8, above. The number ofCTCs (i.e., CK+/CD45− nucleated cells), the number of CK−/CD45−nucleated cells, the expression of FOLR1 on CTCs, the number ofCK−/CD45− nucleated cells, and the percentage of FOLR1 positive CTCs andCK−/CD45− nucleated cells are determined by LSC for each sample. Thedata is used to determine FOLR1 expression levels in CTCs at varioustime points during the Phase I clinical trial for IMGN853.

All publications, patents, patent applications, internet sites, andaccession numbers/database sequences (including both polynucleotide andpolypeptide sequences) cited herein are hereby incorporated by referencein their entirety for all purposes to the same extent as if eachindividual publication, patent, patent application, internet site, oraccession number/database sequence were specifically and individuallyindicated to be so incorporated by reference.

What is claimed is:
 1. A method of detecting FOLR1 protein in a samplecomprising contacting said sample with an antibody or antigen-bindingfragment thereof wherein the antibody or antigen-binding fragment bindsto the same FOLR1 epitope as an antibody selected from the groupconsisting of: (a) an antibody comprising the variable heavy chainpolypeptide of SEQ ID NO: 25 and the variable light chain polypeptide ofSEQ ID NO: 29; and (b) an antibody comprising the variable heavy chainpolypeptide of SEQ ID NO: 26 and the variable light chain polypeptide ofSEQ ID NO:
 30. 2. The method of claim 1, wherein said sample is a cancersample and said cancer is selected from the group consisting of:ovarian, non-small cell lung cancer, uterine, endometrial, pancreatic,renal, lung, cancer of the peritoneum, and breast cancer.
 3. The methodof claim 1, wherein said antibody or antigen-binding fragment thereofused to detect FOLR1 protein is a murine, chimeric, humanized, orresurfaced antibody or antigen-binding fragment thereof.
 4. The methodof claim 1, wherein said antibody or antigen-binding fragment thereofused to detect FOLR1 protein binds to a human folate receptor 1 with aKd of about 1.0 nM to about 10 nM.
 5. The method of claim 1, wherein theantibody or antigen-binding fragment thereof used to detect FOLR1protein comprises a detection agent.
 6. The method of claim 5, whereinthe detection agent is a chromogenic detection agent, a fluorogenicdetection agent, an immunofluorescent detection agent, an enzymaticdetection agent, or an electr chemiluminescent detection agent.
 7. Themethod of claim 1, wherein the antibody or antigen-binding fragmentbinds to the same FOLR1 epitope as an antibody comprising the variableheavy chain polypeptide of SEQ ID NO: 25 and the variable light chainpolypeptide of SEQ ID NO:
 29. 8. The method of claim 1, wherein theantibody or antigen-binding fragment binds to the same FOLR1 epitope asan antibody comprising the variable heavy chain polypeptide of SEQ NO:26 and the variable light chain polypeptide of SEQ ID NO:
 30. 9. Themethod of claim 1, wherein the FOLR1 protein is detected using anantibody or antigen-binding fragment thereof, which comprises variableheavy chain CDR1, CDR2, and CDR3 and variable light chain CDR1, CDR2,and CDR3 amino acid sequences selected from the group consisting of: (a)SEQ ID NOs: 1, 2, and 3 and SEQ ID NOs: 13, 14, and 15, respectively;and (b) SEQ ID NOs: 4, 5, and 6 and SEQ ID NOs: 16, 17, and 18,respectively.
 10. The method of claim 9, wherein the FOLR1 protein isdetected using an antibody or antigen-binding fragment thereof thatcomprises variable heavy chain CDR1, CDR2, and CDR3 and variable lightchain CDR1, CDR2, and CDR3 amino acid sequences comprising SEQ ID NOs:4, 5, and 6 and SEQ ID NOs: 16, 17, and 18, respectively.
 11. The methodof claim 9, wherein the FOLR1 protein is detected using an antibody orantigen-binding fragment thereof that comprises the variable heavy chainpolypeptide of SEQ ID NO: 25 and the variable light chain polypeptide ofSEQ ID NO:
 29. 12. The method of claim 9, wherein FOLR1 protein isdetected using an antibody or antigen-binding fragment thereof thatcomprises the variable heavy chain polypeptide of SEQ ID NO: 26 and thevariable light chain polypeptide of SEQ ID NO:
 30. 13. The method ofclaim 9, wherein the sample is a cancer sample.
 14. The method of claim9, wherein the FOLR1 protein is detected using an antibody orantigen-binding fragment thereof that comprises variable heavy chainCDR1, CDR2, and CDR3 and variable light chain CDR1, CDR2, and CDR3 aminoacid sequences comprising SEQ ID NOs: 1, 2, and 3 and SEQ ID NOs: 13,14, and 15, respectively.
 15. The method of claim 9, wherein the FOLR1protein is detected using an antibody that comprises the heavy chainamino acid sequence of SEQ ID NO: 33 and the light chain amino acidsequence of SEQ ID NO:
 37. 16. The method of claim 9, wherein the FOLR1protein is detected using an antibody that comprises the heavy chainamino acid sequence of SEQ ID NO: 34 and the light chain amino acidsequence of SEQ ID NO:
 38. 17. The method of claim 9, wherein the FOLR1protein is shed FOLR1 protein.
 18. The method of claim 9, wherein thesample is a bodily fluid sample.
 19. The method of claim 13, furthercomprising administering to a patient with a FOLR1-positive cancer anactive agent comprising a FOLR1 antibody or antigen-binding fragmentthereof with the variable heavy chain sequence of SEQ ID NO: 46 and thevariable light chain sequence of SEQ ID NO:
 48. 20. The method of claim13, wherein the FOLR1 protein is shed FOLR1 protein.
 21. The method ofclaim 13, wherein the sample is a bodily fluid sample.
 22. The method ofclaim 19, wherein the active agent comprises a FOLR1 antibody comprisinga heavy chain comprising the same amino acid sequence as the amino acidsequence of the heavy chain encoded by the plasmid deposited with theAmerican Type Culture Collection (ATCC) as PTA-10772 and a light chaincomprising the same amino acid sequence as the amino acid sequence ofthe light chain encoded by the plasmid deposited with the ATCC asPTA-10774.
 23. The method of claim 19, wherein the active agentcomprises the FOLR1 antibody or antigen-binding fragment thereofconjugated to a cytotoxic agent.
 24. The method of claim 22, wherein theactive agent comprises the FOLR1 antibody or antigen-binding fragmentthereof conjugated to a cytotoxic agent.
 25. The method of claim 23,wherein the active agent comprises the FOLR1 antibody or antigen-bindingfragment thereof conjugated to the maytansinoid DM4 via the cleavablesulfo-SPDB linker.
 26. The method of claim 24, wherein the active agentcomprises the FOLR1 antibody or antigen-binding fragment thereofconjugated to the maytansinoid DM4 via the cleavable sulfo-SPDB linker.27. The method of claim 26, wherein the cancer is ovarian cancer.